Types of Waves Pulses are di - Ministry of Education, Guyana

1

MINISTRY OF EDUCATION

SECONDARY ENGAGEMENT PROGRAMME

PHYSICS

TERM 3

GRADE 10

WEEK 1 LESSON 1

TOPIC: Types of Waves

Pulses are disturbances and the type of pulse obtained depends on what causes the disturbance

and what is being disturbed. A continuous production of pulses gives rise to a progressive wave.

Progressive waves are caused by vibratory motion.

This can be demonstrated using a spring or slinky.

2

Classes of waves: Transverse and Longitudinal

Transverse waves

Transverse waves are ones in which the displacement of the particles is at right angles to the

direction of travel of the wave motion.

If one end of a slinky is clamped stationary and the other end is waggle side to side, you will see

the slinky moving in the same way as your hand movement. The wave moves in one direction

and the oscillations of the slinky are perpendicular to that direction.

Longitudinal waves

Longitudinal waves are ones in which the displacement of the particles is in line with or parallel

to the direction of travel of the wave motion.

If you push and pull one end of the slinky repeatedly you will notice that the parts move

backwards and forwards in line with the direction in which the wave is moving.

3

A ripple tank can also be used to observe waves.

If a pencil is dipped into the water without touching the bottom or shaking the tank, the pulses

create waves which have a circular wavefront.

If a bar (for example, a straight piece of wood) is used, the waves produced are called plane

surface waves in water.

4



PHYSICS

TERM 3

GRADE 10

WEEK 1 LESSON 1 Worksheet

1 Differentiate between longitudinal and transverse waves.

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

Select the letter next to the correct answer for each of the following questions.

2 The particles of the medium are in periodic motion, perpendicular to the direction of

propagation of the energy.

Which of the following terms is defined by the above statement?

(A) longitudinal pulse (B) longitudinal wave

(C) torsional pulse (D) transverse wave

5

The following diagram shows different points labelled on a wave.

3 Which one of the labelled points is in phase with point H?

(A) K (B) L (C) O (D) P

4The particles of the medium are in periodic motion parallel to the direction of propagation of

the energy.

Which of the following terms is defined by the above statement?

(A) longitudinal pulse (B) longitudinal wave

(C) torsional pulse (D) transverse pulse

5 A transverse wave is travelling through a medium. The particles of the medium are moving

(A) parallel to the direction of travel of the wave

(B) antiparallel to the direction of travel of the wave

(C) perpendicular to the direction of travel of the wave

(D) backwards and forwards in the direction of travel of the wave

6



PHYSICS

TERM 3

GRADE 10

WEEK 1 LESSON 2

TOPIC: Wave Parameters

Amplitude, a, is the height of a crest or the depth of a trough measured from the undisturbed

position. It is the maximum displacement of a particle from that position.

Speed, v, is the distance moved forward by a crest or trough in one second. This is the speed of

propagation or travel of the wave.

Frequency, f, is the number of waves passing any given point in one second or the number of

complete vibrations made in one second.

Wavelength, λ, is the distance between two adjacent or successive crests or troughs

Period, T, is the time taken for a particle to make one complete to and fro oscillation.

7

Wave speed, wavelength and frequency are related by the equation

Speed = frequency x wavelength

v = f λ

where speed is measured in metres per second (ms-1) ;

frequency is measured in hertz (Hz) or s-1 ;

wavelength is measured in metres (m)

The period of a wave and its frequency are related by the equation:

Period = 𝟏

𝒇𝒓𝒆𝒒𝒖𝒆𝒏𝒄𝒚

T = 𝟏

𝒇

where period is measured in seconds (s) and

frequency is measured in hertz (Hz) or s-1.

Worked examples

1 A wave has frequency of 50 Hz and a wavelength of 10 m. What is the speed of the wave?

Speed = frequency x wavelength

v = f λ

v = 50 Hz x 10 m

v = 500 ms-1

2 A wave has frequency of 5 Hz and a speed of 25 ms-1. What is the wavelength of the

wave?

v = f λ

λ = =

λ = 5 m

8

3 A wave has wavelength of 10 m and a speed of 340 ms-1. What is the period of the wave?

v = f λ

f = = =

f = 34 s-1 or 34 Hz

T = =

T = 0.03 s

9



PHYSICS

TERM 3

GRADE 10


1 The wavespeed equation is given as v = λf. Complete the table below relating to variables

of this equation.

Quantity symbol Quantity term Unit Unit symbol

v Wavespeed

λ metre

f Hz

2 A wave with a frequency of 14 Hz has a wavelength of 3 m. At what speed will this wave

travel?

3 The speed of a wave is 65 ms-1. If the wavelength of the wave is 0.8 m, what is the

frequency of the wave?

10

4 A wave with a frequency of 500 Hz is travelling at a speed of 200 ms-1. What is the

wavelength?

5 A period of 0.005 s yield a frequency of ___________.

11



PHYSICS

TERM 3

GRADE 10

WEEK 1 LESSON 3

TOPIC: Graphs representing waves

There are two types of graphs that can be drawn to represent a wave.

1. The displacement – position graph

2. The displacement – time graph

The displacement – position graph is like a photograph of a transverse wave at one instant in

time. It gives information about the displacements at different positions along the wave train at a

particular instant.

A displacement – position graph provides the amplitude and wavelength of the wave.

12

A displacement – time graph shows the behaviour of a single particle over a period of time. It

shows how the displacement of the particle changes as a wave passes.

A displacement – time graph provides the period of the wave. The frequency can be calculated

by inversing the value of the period.

13



PHYSICS

TERM 3

GRADE 10


1 The property of the wave which is labelled x in the diagram is called the

(A) amplitude (B) frequency

(C) velocity (D) wavelength

2 A wave train is shown below.

The wavelength is equal to the length of

(A) the line segment PQ

(B) the line segment PR

(C) the line segment PS

(D) the line segment SW

14

3 Which of the following properties of a wave is independent of all the others?

(A) amplitude (B) frequency

(C) period (D) velocity

4 The following diagram shows a transverse wave. Use a ruler to take any necessary

measurements.

The wavelength of this wave is approximately

(A) 2 cm (B) 4 cm (C) 6 cm (D) 12 cm

5 The following diagram shows a transverse wave. Use a ruler to take any necessary

measurements.

The amplitude of this wave is approximately

(A) 1.5 cm (B) 4 cm (C) 6 cm (D) 12 cm

15

Questions 6 – 8 refer to the wave shown below.

6 What is the amplitude of the wave? __________

7 What is the period of the wave? ____________

8 What is the frequency of the wave? _________

Questions 9 and 10 refer to the wave shown below.

9 The amplitude of the wave is ________.

10 The frequency of the wave is ________.

16



PHYSICS

TERM 3

GRADE 10

WEEK 2 LESSON 1

TOPIC: Behaviour of water waves

Reflection – the bouncing off of a wave from a barrier. Only the direction of the wave changes during reflection.

The source O corresponds to the object and the virtual source I of the reflected waves corresponds to the virtual image formed by a plane mirror. OM = MI and IO is at right angles to the reflector.

Refraction – the change of direction of a wave as it passes from one medium to another. During refraction, there is a change in speed, direction and wavelength, but not the frequency.

17

Diffraction – is the spreading of waves which occurs when a wave goes around an obstacle or through a gap. There is only a change in direction, not in velocity, frequency or wavelength.

A wide gap produces wavefronts that are straight except for a slight edge curvature. A narrow gap produces circular wavefronts.

Interference – the interaction of two or more waves of the same frequency emitted by coherent sources.

If the waves are in phase, they may reinforce one another (constructive interference). If they are out of phase, they tend to cancel each other out (destructive interference).

18



PHYSICS

TERM 3

GRADE 10


Briefly define the terms: reflection, refraction, diffraction and interference as they relate to

waves.

Reflection: ____________________________________________________________________

______________________________________________________________________________

Refraction:____________________________________________________________________

______________________________________________________________________________

Diffraction:____________________________________________________________________

______________________________________________________________________________

Interference:__________________________________________________________________

______________________________________________________________________________

19

The figures below show the same wave striking a plane reflecting surface and incident on a small gap in a plan, reflecting surface respectively. Complete the diagrams to show the wave (i) after reflection and (ii) after passing through the gap.

Reflection Diffraction

The figure below shows the same wave approaching the gap which has been increased to five times its original size. Complete the figure to show the wave after it has been passed through the gap.

20



PHYSICS

GRADE 10

WEEK 2 LESSON 2

TOPIC: Sound Waves – Production and Propagation

Vibrating systems produce sound. The table below gives examples of musical instruments and

the vibrating system linked with them.

Musical instrument Vibrating system

Guitar Strings

Drum Stretched skin

Flute Column of air

Whistle (without ball) Air

Tuning fork Prongs

The vibrating systems affect the particles of the medium in which they vibrate. Sound is

propagated as a longitudinal wave and the sound energy moves in a set of compressions and

rarefactions.

Sound waves cannot be transmitted through a vacuum since it requires particles or matter to be

transmitted.

21

Activity to demonstrate that sound is not transmitted in a vacuum.

1. Hang an electric bell under a bell jar using flexible cords. An electric bell with a visible

hammer and gong is preferred but any type can work, even an alarm clock.

2. Connect the electric bell to an external power source with a switch.

3. Seal the bell jar to a flat piece of metal using grease or sealing wax. The metal plate

should have an outlet to which a vacuum pump is connected.

4. Close the switch and observe the hammer. Listen for a sound from the electric bell.

5. Now turn on the vacuum pump and while the pump is removing the air, observe the

hammer and listen to the bell.

Before the vacuum pump is turned on, air is in the bell jar. A sound is heard as the hammer hits

the gong. However, when all the air is pumped out of the bell jar, no sound comes from the bell

even though it can be seen that the hammer continues to strike the gong. This shows that sound is

not transmitted in a vacuum and a material medium is necessary.

Some air may remain under the jar and result in a faint sound being heard. Incomplete damping

may also result in some sound escaping.

22



PHYSICS

GRADE 10


1 Fill in each of the blanks with an appropriate word.

Sound is made when objects ______1_______. For example, in the guitar it is the

_______2______ which ______3_______, in the tuning fork it is the __________4________

which _______5________.

Sound is transmitted as a _________6_________ wave. When sound passes through a medium it

does so by a series of ________7_________ and __________8___________. Sound can be

transmitted through solids, _________9__________ and _________10__________ but it cannot

be transmitted through a __________11__________.

2 Describe a simple experiment to demonstrate that sound requires a medium to be

transmitted.

23



PHYSICS

GRADE 10

WEEK 2 LESSON 3

TOPIC: Properties of sound waves

The frequencies detectable by the human ear are in the range 20 Hz to 20 kHz. However, the

exact range will vary from person to person. The range of audibility decreases with age.

Sound can be classified as either a pure note, a musical note or noise. When the sound is

composed of a single frequency, these are usually pleasing to the ear.

Musical notes have three properties:

1. Pitch

2. Loudness

3. Quality

The pitch of a note refers to its position in a musical scale. It is a measure of how high or low the

note sounds. The pitch is related to the frequency of the wave. As the frequency increases, the

pitch also increases.

Loudness: this is the magnitude of the sensation produced when a sound reaches the ear. The

loudness is related to the amplitude of the wave. The larger the amplitude of the vibrating source,

the louder is the sound heard.

Quality: this property distinguishes between musical notes of the same frequency played on

different instruments. The way an instrument sounds is called its quality or tone.

Sound may be a mixture of frequencies which are not overtones and may be unpleasant to the

ear. It is then classified as noise.

24



PHYSICS

GRADE 10


Fill in each of the blanks with an appropriate word.

The range of frequency detected by the human ear is from _______1________ to

_________2_______. When we increase the frequency of a sound, the _______3________ of the

sound increases. If the amplitude of the sound increases, the _______4_______ of the sound

increases. When the overtones of a note varies, the ________5_________of the sound varies.

The _______6_______ of a sound is the magnitude of the sensation produced when a sound

reaches the ear. The ________7________ of a sound is how high or low the note sounds or is

positioned in a musical note. The way an instrument sounds is called its tone or

________8______.

25



PHYSICS

GRADE 10

WEEK 3 LESSON 1

TOPIC: Speed of sound

The speed of sound is approximately 300 ms-1. This value may be higher and depends on the

temperature and pressure of the air.

Sound travels slower than light (speed of light is approximately 3 x 108 ms-1).

Measuring the speed of sound using echoes.

1. Stand 100 m at right angles to a large wall.

2. Make a sharp clapping sound by striking two blocks of wood against each other.

3. Adjust the rate of clapping in such a way that a clap coincides with the return of the echo

from the wall. Maintain this rate of clapping.

4. Starting at zero as a stopwatch is started, count the number of claps and stop the

stopwatch at 50 or 100 claps.

Use the formula, speed = 𝒅𝒊𝒔𝒕𝒂𝒏𝒄𝒆 𝒕𝒓𝒂𝒗𝒆𝒍𝒍𝒆𝒅

𝒕𝒊𝒎𝒆 𝒕𝒂𝒌𝒆𝒏 to calculate the speed of sound.

26

Example of calculation:

Distance from wall = 100 m

Distance sound travels = 200 m

Time taken for 50 claps = 30.3 s

Time interval between claps = .

= 0.606 s

speed =

speed =

. = 330 ms-1

Worked example

Someone is standing 1 km away from a church. Estimate the time taken for the sound of the

church bell to reach the person. [Use speed of sound = 33 m s-1]

1 km = 1 000 m

Using formula, speed =

Time taken =

=

= 3.03 s

27



PHYSICS

GRADE 10


1 A person standing 45 m from the foot of a tall cliff claps his hand and hears an echo

0.25 s later. Calculate the velocity of sound in air.

2 In a simple experiment to determine the speed of sound, the student with a stopwatch

stands on a flat stretch of sand and a teacher standing at a measured distance of 400 m

fires a pistol. The student starts his stopwatch when he sees the flash of the pistol and

stops it when he hears the sound of the shot. The time intervals, in seconds, obtained for

three experiments are: 1.0, 1.2 and 1.1.

Calculate a value for the speed of sound in air.

28



PHYSICS

GRADE 10

WEEK 3 LESSON 2

TOPIC: Behaviour of sound waves

Reflection of sound waves

Sounds waves can be reflected just like any other wave. Smooth and rigid surfaces cause the

strongest reflections. The reflected sound waves are called echoes.

Activity to demonstrate the reflection of sound

Mount one of the cardboard tubes in the retort stand. Direct the tube towards a smooth hard wall

surface. Put the watch at the end of the tube away from the wall. Mark where the beam is

expected to strike the wall.

Use the other tube to detect where the reflected sound should be. Do this by directing one end of

the tube at the spot on the wall where the beam of sound from the watch is expected to strike the

wall. Then with this end directed at the wall, put your ear at the other end of the tube and move

the tube around until you get a position where the reflected sound is heard the loudest.

29

Refraction of sound waves

Sound waves can change direction when they move from one material to another due to a change

of speed. When sound moves through different layers of air, the sound waves bend as they travel

through layers of air at different temperatures. This effect is most noticeable at night when the air

near the ground is cooler than the air above it.

Sound waves can follow a curved path through a temperature gradient.

Diffraction of sound waves

Sound waves are easily diffracted by larger gaps due to a large wavelength. Sound waves will

spread as they pass through doorways or around corners as their wavelength is similar to the size

of these gaps.

Interference of sound waves

When two sound waves meet, they interfere. The waves are superimposed on top of each other.

If the two sources producing an identical signal are used then this effect can be detected. Two

loudspeakers connected to the same source will form an interference pattern in front of them.

This pattern will have regions where the waves destructively interfere and no sound will be

heard. There will also be regions where the two waves constructively interfere and the sound will

be louder than normal.

30



PHYSICS

GRADE 10


Fill in each of the blanks with an appropriate word.

Sound is a wave and therefore exhibits all properties of waves. It can therefore be

___________1_________, ___________2____________, ____________3__________ and it

shows interference. We sometimes hear an echo of a sound. This is possible because sound

exhibits the property of ________4_________. On a day when the ground is very hot and the

lower layers of the air are the hottest, it is more difficult to hear over long distances. This

happens because sound exhibits the property of _________5_________. The sound waves are

_________6_________ upwards away from the ground. Sound can be heard coming from a

building on the far side and sound coming from an open door can be heard in any direction. This

is true because sound exhibits the property of _________7____________.

31



PHYSICS

GRADE 10

WEEK 3 LESSON 3

TOPIC: Ultrasound

High frequency sounds (above 20 kHz) are not detectable by humans and so are called

ultrasound. The Latin word ultra means ‘beyond’. Animals such as bats and dolphins produce

ultrasound pulses to detect obstacles.

Ultrasound behaves in the same way as ordinary sound. The effect that is most often used,

however, is that of reflection. It would be extremely difficult to produce the other effects

practically, since the wavelengths involved are so very small.

Ultrasound is used to determine the depth of bodies of water. The frequencies used in depth –

sounding are high, at about 50 kHz. The high frequency means that the wavelength is very short,

so that there is little diffraction or spreading of the ultrasound wave energy. This means that a

beam of ultrasound energy can be made more directional; it can be ‘aimed’ much better than

ordinary sound.

32

Another important application of ultrasound is in medical imaging. It is also used in medicine

very routinely nowadays to provide images for diagnoses and for monitoring. The gender of a

foetus of an unborn child can be predicted with the use of ultrasounding.

Worked example

A ship sends a pulse of ultrasound and receives an echo 0.3 seconds later. If the speed of sound

in water is 1500 ms-1, calculate its depth.

Speed =

Distance = Speed x Time taken

Distance = 1500 ms-1 x 0.3 s = 450 m

Depth = ½ x Distance = ½ x 450 m = 225 m

33



PHYSICS

GRADE 10


Ultrasound maybe used in determining the growth of a baby in its mother’s womb. Sound pulses

are directed towards the baby’s skull and reflected pulses echoes from the front and back of the

baby’s skull are detected and displayed on an oscilloscope screen, as shown below.

(a) In terms of the distances a and d, write an expression for

(i) the distance travelled by the sound pulse after reflection from the front of the skull to the

sound detector.

(ii) the distance travelled by the sound pulse after reflection from the back of the skull to the

sound detector.

34

(b) The oscilloscope screen shows that the time between the first and second echo is 0.11 ms.

The speed of the sound pulses is 1200 ms-1.

(i) Determine the difference in distance travelled between the first and second echo.

(ii) the diameter, d, of the baby’s skull.

35



PHYSICS

GRADE 10

WEEK 4 LESSON 1

TOPIC: Electromagnetic waves (e.m. waves)

Electromagnetic radiation is an example of transverse wave because it involves electric and

magnetic fields oscillating perpendicular to the direction in which the radiation is travelling. All

e.m. waves travel with equal speed in a vacuum. The character of an e.m. wave is determined by

its frequency. Waves in the electromagnetic spectrum are grouped into six major regions based

on their wavelengths or how they are produced.

Common properties of electromagnetic radiation

All e.m. radiations share some common properties and behaviours. All e.m. waves

1. transfer energy from one place to another

2. can be emitted and absorbed by matter

3. do not need a medium to travel through

4. travel at 3.0 x 108 ms-1 in a vacuum

5. are tranverse waves

6. obey the laws of reflection and refraction

7. can be superposed and produce interference effects

8. can be diffracted.

36

The Electromagnetic Spectrum

37

Sources and Uses of Electromagnetic Waves

Electromagnetic wave Sources Uses

Radio waves Electron movements in

transmitter circuits of TV and

radio systems

Communication such as radio

or television. Microwaves are

used to cook food.

Infra – red radiation Any warm or hot object.

Infra – red cameras (often

used for seeing during the

night).

Infra – red thermometers to

measure temperature without

contact.

Visible light Very hot objects.

Some chemical reactions.

Photography.

Lasers.

Sight.

Ultraviolet light Very hot objects (such as the

Sun).

Fluorescent lamps containing

mercury.

Forensic science.

Chemical analysis.

Sterilisation of equipment.

38

Electromagnetic wave Sources Uses

X – rays X – ray tubes which propel

fast electrons into metal

blocks.

Forming images of bones in

the body.

High – energy X – rays can

be used to find damage in

other materials.

Gamma rays Decay of radioactive

materials.

Nuclear explosions.

Gamma ray bursts from

cosmic events such as

formation of black holes.

Cancer treatment

(radiotherapy).

Gamma emitters are used as

radioactive tracers in

medicine or other

applications.

Sterilisation of equipment or

some food.

39



PHYSICS

GRADE 10


Five kinds of electromagnetic radiations are given below. Choose the correct one for each of the

uses in questions 1 to 4.

(A) Infra – red

(B) X – rays

(C) Ultraviolet

(D) Gamma rays

(E) Radiowaves

1 The examination of metal castings for faults

2 The detection of oil painted forgeries

3 Using a radio for communication

4 Checking for injuries to a bone

Use an appropriate word for each of the blanks below.

In a vacuum, electromagnetic waves all have the same ______5_______. Light waves have a

greater ____6____ than radiowaves. Another type of electromagnetic radiation is _____7______

and this found in _____8_________.

The electromagnetic wave with the shortest wavelength is _______9______ and the

electromagnetic wave with the lowest frequency is __________10_________.

40



PHYSICS

GRADE 10

WEEK 4 LESSON 2

TOPIC: Theories of Light

For many centuries, much speculation existed about the true nature of light. The debate became

particularly lively in the 17th century when Descartes, a French scientist, formulated two

opposing theories to explain the nature of light. The two theories are the particle theory and the

wave theory. Some of the leading scientists of the time became actively involved in the debate,

either supporting Descartes’ particle theory or his wave theory.

The Particle Theory

Descartes’ particle theory described light as being made up of small particles moving linearly.

He used this assumption to explain refraction and reflection of light. His explanation for

refraction was that when light particles were incident on the surface of separation between two

media, their velocity components in the direction perpendicular to the surface increased as the

particles went from the less dense to the more dense transparent material while that parallel to

the surface remained constant. This resulted in an increase in the resultant velocity and the

bending of light. He theorised that reflection was due to the rebounding of the particles of light

when incident on a barrier.

Descartes’ particulate theory was supported and further developed by Sir Isaac Newton in his

OPTICKS, published in 1704. Newton believed that light was made up of a stream of tiny

particles travelling at very high speeds, in straight lines. The motions of these particles produced

vibrations in the surrounding fluid, called ether, that was thought to fill all of space. The

vibrations were believed to be capable of reinforcing or hindering the motion of the light

41

particles. He explained partial reflection at a boundary by saying that the particles which were

reinforced could pass through and those which were hindered were rebounded.

The Wave Theory

Descartes also proposed that light could be due to pressure or action transmitted from the object

seen to the eye through the matter or a surrounding space.

Huygens was another supporter of the wave theory. He thought of light as luminous energy due

to a vibrating source which produced longitudinal waves in all directions in the space around the

source. As the wave touches points in its paths it causes them to vibrate longitudinally sending

out secondary wavelets. The sum of the wavefronts of these secondary wavelets form an

envelope that is the new wavefront of the wave.

Descartes used his particle theory to explain refraction and reflection, but it could not be used to

explain diffraction.

In the 18th century, the debate centered on the more developed theories of Newton and Huygens.

The central issue was that the particle and wave theories predicted opposite effects on the speed

of light going from air to water. Newton predicted that the speed should be greater in the more

dense medium while Huygens predicted it should be less. Support for Huygens’s theory came

from Foucault who actually measured the speed of light in air and water and found that it was

less in water. As a result of Foucault’s experiment, Newton’s theory was discarded in favour of

Huygens’.

42



PHYSICS

GRADE 10


1 Research on the theories of light.

Present your findings in a suitable table to compare the theories.

2 Compare the rival theories of light held by the scientists: Huygens, Newton, Young and

Einstein.

43



PHYSICS

GRADE 10

WEEK 4 LESSON 3

TOPIC: Young’s Interference Experiment and the Wave Theory

In 1802 Thomas Young performed what is now called the Young’s slits experiment. In this

experiment, two coherent beams of light cross each other’s path to produce an observable

interference patter.

Each slit is needed to cause diffraction and the diffracted beams produce the interference. Where

the wave overlap superposition enables constructive or destructive interference to result in an

unchanging pattern. When crests (or troughs) overlap a bright spot is obtained because there is

constructive interference. When a crest and a trough overlap, darkness or destructive interference

occurs.

We can do a similar experiment as follows (in a room that can be blacked – out)

1. Blackened one side of a glass slide by holding it in the smoke of a candle flame or by

treating one surface of the slide with aquadag.

2. To make the pair of slots, hold two razor blades together with their edges parallel and

pull them along the blackened surface of the glass slide. The slits will be very close

together (less than 0.5 mm apart). Mount the slide in a retort clamp so that the slits are

vertical.

3. Set up a straight filament lamp in another stand about 50 cm in front of the slits so that

the filament is parallel to the slits.

4. Set up (also in the clamp) a sheet of red filter between the lamp and slits.

44

5. Make the screen by taping a sheets of greaseproof paper over a stiff cardboard frame

about 20 cm square. Support this screen in a clamp about 1 m behind the plane of the slits

and parallel to it.

6. Check to ensure that the line joining the source and the slits is perpendicular to the plane

of the screen.

7. Switch on the straight filament lamp.

8. Use a high – power magnifier (a thick convex lens) to view the interference pattern from

behind the screen. This pattern should be a series of red and dark bands (which Young

called ‘fringes’).

Young’s slits experiment

45

The Resulting Interference Pattern

46



PHYSICS

GRADE 10


1 Describe a simple experiment to demonstrate the interference of light waves.

State TWO precautionary steps that should be taken to ensure the accuracy of the results.

2 Complete the diagram below to demonstrate the interference of waves.

47



PHYSICS

GRADE 10

WEEK 5 LESSON 1

TOPIC: Wave – Particle Duality of Light

Prior to the 20th century, scientists regarded particles and waves as having mutually exclusive

properties. Particles were thought to have mass and to occupy definite volumes, while waves

were a means of transferring energy and were spread out in space. Earlier experiments, like

Young’s double slit experiment had shown doubt that light had wave nature. Light exhibited the

known properties of waves.

It was not until the beginning of the 20th century that the idea of light having BOTH wave and

particle properties was considered.

In 1888 the Photoelectric Effect was discovered. When light was shone on some metal surfaces,

free electrons near the surface were emitted. These electrons were emitted almost

instantaneously and the number of electrons emitted increased with the intensity of the light, but

electrons were NOT emitted for all wavelengths of light.

In 1900 Planck introduced the idea that energy is not emitted from a body continuously but in

discrete units called QUANTA (That is, it has a particle nature).

In 1905 Einstein applied the “Quantum theory” to light and used it to explain the photoelectric

effect. In 1916 this theory was supported by experiments done by Millikan.

The wave – particle duality of light was further supported by the fact that spectral lines of

gaseous elements have discrete wavelengths and are caused by quanta or photons of light being

48

emitted or absorbed by movement of electrons among discrete energy levels. With conclusive

evidence that light has both particle and wave properties, the dual nature of light is now

accepted.

49



PHYSICS

GRADE 10


In the seventeenth century, two conflicting theories concerning the nature of light were put forward.

State what these theories considered light to be.

Theory A: ____________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

Theory B: ____________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

Indicate, by ticking the relevant boxes, the properties which these theories can explain. Place an X in the box if theory CANNOT satisfactorily explain the property.

Property Theory A Theory B Travels in a straight line

Reflection

Conveys energy

Diffraction

50



PHYSICS

GRADE 10

WEEK 5 LESSON 2

TOPIC: Rays of Light

Diffraction of light

Diffraction occurs when a wave spreads out after passing through a gap or around an obstacle.

This is only observed when the dimensions of the gap or obstacle is comparable to the

wavelength of the wave. Light has a range of wavelengths from about 3 x 10-7 m to 7 x 10-7 m,

which is extremely small compared to the dimensions of everyday objects. For diffraction of

light to be observed, the gap or obstacle must have dimensions approaching 10-6 m.

Light rays and shadows

Photons leaving a light source travel in straight lines called rays. These rays are the paths or

directions along which the energy flows.

Evidence that light travels in straight lines is found in the formation of shadows and eclipses, the

formation of images by pinhole cameras and the fact that we cannot see around corners.

A shadow is formed when an opaque object is placed in the path of a beam of light rays. The

type of shadow formed depends on whether the light comes from a point source or an extended

source.

Umbra – the total or sharp shadow behind an opaque object where no light has reached. This

type of shadow is formed by point sources and has a clearly defined outline.

51

Penumbra – the area of a blurred or fuzzy shadow around the edges of the umbra. This type of

shadow is formed by larger, spread out sources of light. It is an area where a small amount of

light has reached.

Shadow formed from point source of light

Shadows formed from extended source of light

52



PHYSICS

GRADE 10


1 Define the term diffraction and briefly describe why the diffraction of light is normally

observed.

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

2 Using appropriate diagrams, differentiate between the terms umbra and penumbra.

______________________________________________________________________________

______________________________________________________________________________

53



PHYSICS

GRADE 10

WEEK 5 LESSON 3

TOPIC: Rays of Light

Eclipses

Solar eclipse – occurs when the Moon moves into a position directly between the Sun and the

Earth. As a result a circular shadow is cast on the Earth. Such an eclipse appears as a total eclipse

if it is viewed from the umbra region, or as a partial if viewed from the penumbra region. Solar

eclipses do not happen very often, as although the Moon circles the Earth every 28 days, only

rarely are all three celestial bodies (Sun, Moon and Earth) in a straight line.

Solar eclipse

Lunar eclipse – occurs when the Earth moves into a position directly between the Sun and the

Moon. As a result, an area of full shadow totally covers the Moon. Normally, the Moon is out of

line with the Earth, and the Sun’s light falls on it to give a full moon.

Lunar Eclipse

54

Pinhole camera – is the simplest form of camera, consisting of a box with a pinhole at one end and a screen made of tracing paper at the other end. An inverted (upside down) real image of an object forms on this screen. If the pinhole is made larger, the image becomes brighter but also becomes blurred. This is because a large pinhole acts like lots of small pinholes, each producing an image in a slightly different position.

Image formation by a pinhole camera

Making a pinhole camera

The inside surfaces of a sturdy cardboard box are lined with black paper. A small circular hole

about 5 cm diameter is cut in the front of the box and a piece of thin, stiff cardboard or black

paper is pasted over the hole. A tiny hole is then made in the centre of this card or black paper

with a sewing needle. The cardboard at the back of the box is cut away and a sheet of cumple –

free white tracing paper or greaseproof paper is pasted over the opening to serve as a screen. The

box is carefully sealed with tape to make it lightproof.

55



PHYSICS

GRADE 10


Use household items and create a pinhole camera.

Carry out the following investigation using your pinhole camera:

1) Measure the size of the lamp or candle (object height)

2) Measure the size of the image formed on the screen (image height)

3) Measure the distance from the object to the pinhole (object distance)

4) Measure the distance from the image to the pinhole (image distance)

Calculate

(i)

(ii)

Compare the two ratios.

What quantity did you calculate in parts (i) and (ii) above?

57

SOLUTIONS TO WORKSHEET QUESTIONS

WEEK 1 LESSON 1 Worksheet Answers

1 A longitudinal wave is a progressive wave in which the oscillation or vibration is along

the line of the direction in which the wave is travelling. A transverse wave is a

progressive wave in which the oscillation or vibration is at right angles to the direction in

which the wave is travelling.

2 D

3 C

4 B

5 C


1

Quantity symbol Quantity term Unit Unit symbol

v Wavespeed metre per second ms-1

λ Wavelength metre m

f Frequency Hertz Hz

2 42 ms-1

3 81.25 Hz

4 0.4 m

5 200 Hz

58


1 A

2 D

3 A

4 B

5 A

6 4 cm

7 4.0 s

8 0.25 Hz

9 10 cm

10 2.5 Hz

59


60


Answers to the fill in the blanks question.

1 vibrate

2 strings

3 vibrate

4 prongs

5 vibrate

6 longitudinal

7 compressions

8 rarefactions

9 liquids

10 gases

11 vacuum

61


1 20 Hz

2 20 kHz

3 pitch

4 loudness

5 quality

6 loudness

7 pitch

8 quality


1 360 ms-1

2 364 ms-1


1 reflected

2 refracted

3 diffracted

4 reflection

5 refraction

6 refracted/bent

7 diffraction

62


(a)(i) Distance = a

(a)(ii) Distance = d + a

(b)(i) Distance travelled between echoes = 0.132 m

(b)(ii) Diameter of skull = 0.066 m or 6.6 cm


1 D

2 C

3 E

4 B

5 velocity

6 frequency

7 any correct type of em radiation named

8 correct source for named em radiation

9 gamma radiation

10 radio waves

63


2

64


Theory A: Considered light to be minute particles travelling at very high speed.

Theory B: Considered light to be a wave formation in which each point on a wavefront was a source of secondary waves.

Property Theory A Theory B Travels in a straight line

Reflection

Conveys energy

Diffraction X

65


1 Diffraction is the spreading of waves which occurs when a wave goes around an obstacle or through a gap. There is only a change in direction, not in velocity, frequency or wavelength.

Light diffracts when it passes through a gap. The wavelength of light is very small and hence, it is only noticeable when the gaps are very narrow.

2

Umbra – the total or sharp shadow behind an opaque object where no light has reached. This

type of shadow is formed by point sources and has a clearly defined outline.

Penumbra – the area of a blurred or fuzzy shadow around the edges of the umbra. This type of

shadow is formed by larger, spread out sources of light. It is an area where a small amount of

light has reached.


The ratios are expected to be equal.

Quantity calculated is Magnification

1



TERM 3

PHYSICS

GRADE 10


Use the method described in the notes to carry out an investigation regarding the relationship

between the angle of incidence and angle of refraction. Complete the table below using results

from your experiment. Paste the results of your experiment in the space provided.

Angle of incidence, i/0 Angle of reflection, r/0

15

30

45

60

Results:

Using your results, what deduction can you make regarding the relationship between angle of

incidence and angle of reflection?

______________________________________________________________________________

2

WEEK 6 LESSON 2

TOPIC: Reflection of light – Virtual images

A real object is one which ‘gives off’ light either because it is self-luminous or because it reflects

light falling on it from other sources.

A real image is one formed by rays of light which actually meet at a point. Since the rays

forming the real images actually converge to a point, the real images can be focused on a screen.

A virtual image is one formed at the point from which the rays only seem to or appear to diverge.

Since the rays forming the virtual image are divergent, virtual images cannot be focused on a

screen. The image formed from a plane mirror is a virtual image.

3

Experiment to locate a virtual image of a plane mirror

1. Fasten a sheet of paper on a drawing board into which pins can easily be pressed.

2. Mark the reflecting line on the paper, and stand the reflecting surface of a plane mirror

upright on the line.

3. Press an object pin, O, into the board and mark its location.

4. With one eye, view the image I of this pin, then place a sighting pin P1 exactly in line

with the image I and your eye so that the image is covered up.

5. With your eye in the same position, place a second sighting pin P2 so that it covers up

both the object pin’s image I and P1. The image is now known to lie somewhere in line

with P1 and P2.

6. Mark these pin positions and remove the pins.

7. Now view the image I from a different position and repeat the process using sighting pins

P3 and P4.

8. Remove the pins and mirror, draw the lines through P1P2 and P3P4 and also the line

joining the object O and image I.

The image will be found where the two lines cross.

4

Properties of the image formed by a plane mirror:

1. The image is virtual.

2. The image is the same size as the object.

3. The image distance is equal to the object distance.

4. The image is erected or upright.

5. The image is laterally inverted. That is, the left and right are reversed for the image. This

phenomena is very useful. The fronts of emergency vehicles, e.g. the ambulance have the

writing backwards. When this writing is viewed by a driver through the rear – view

mirror, the writing becomes normal.

Lateral inversion of the word AMBULANCE

5


1(a) Use the method described in the notes section to compare the object and image distance

for a plane mirror.

Complete the table below using results from your experiments

Object distance/ cm Image distance/ cm

2

4

6

(b) Using the results from your experiment, what deduction can you make regarding the

object distance and image distance?

______________________________________________________________________________

______________________________________________________________________________

(c) State TWO properties of the image formed by the plane mirror

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

6



TERM 3

PHYSICS

GRADE 10

WEEK 6 LESSON 3

TOPIC: Refraction of light

Refraction is said to occur when light changes direction as it passes from one transparent

medium to another. The diagram below shows refraction as light enters a more optically dense

medium. The ray must enter the second medium at an oblique angle to its surface.

The passage of light rays through a rectangular block and a triangular prism of

transparent material

The angle of refraction (θ2) is the angle between the refracted ray and the normal (N). The angle

of incidence (θ 1) is the angle between the incident ray and the normal, and the angle of

emergence (θ 3) is the angle between the emergent ray and the normal. Note that the emergent ray

7

is parallel to the incident ray (lateral displacement) in the case of the parallel sided (rectangular)

block, but not in the case of the prism.

Two examples of observations which indicate that light can be refracted.

In figure below, a student is standing so that a coin placed in a container is just out of sight.

The coin becomes visible if water is poured into the container. Rays of the light from the coin are

refracted at the surface of the water making the coin appear higher than it actually is.

8

In figure above, water appears to bend a stick as it is half-immersed as shown. The rays of light

from the end of the stick at O are refracted at the surface of the water and so appear to come

from the point I.

Laws of refraction

The laws of refraction are:

-The incident and refracted ray (at the point of incidence) are on OPPOSITE sides (except for

normal incidence) of the normal and ALL lie IN THE SAME PLANE.

-SNELL’S LAW: for light passing from one medium to another, the ratio of the sine of the angle

of incidence to the sine of the angle of refraction is CONSTANT.

E.g. for refraction from medium 1 to medium 2:

1n2 =

= a constant

The refractive index can be given in terms of the ratio of the speed of light in air to the speed of

light in the medium.

9

Problem solving using Snell’s law

1 A ray of light is refracted at the boundary from air to glass. The angle of incidence is 300

and the angle of refraction is 200. Calculate the refractive index of the glass.

n = = = 1.5

2 A ray of light is refracted at the boundary of air to water. The angle of incidence is 250.

What is the angle of refraction? The refractive index of water is 1.33.

n =

sin r =

r = sin-1 ( )

r = sin-1 (.

) = 18.50

10


1 Define the term ‘refraction’

______________________________________________________________________________

2 What are the laws of refraction?

______________________________________________________________________________

______________________________________________________________________________

3 Use Snell’s Law to complete the table below.

Angle of incidence/

degrees

Angle of refraction/

degrees

Refractive index of

boundary

Speed of light in

material/ ms-1

30 1.33

20 1.45

50 30

[Speed of light in air = 3.0 x 108 ms-1]

11



TERM 3

PHYSICS

GRADE 10

WEEK 7 LESSON 1

TOPIC: Refractive Index

Experiment to determine the refractive index of glass

1. Trace the outline of a glass block on a white sheet of paper.

2. Using a protractor, draw a normal, in position as shown in the figure above. Measure

from it several angles of incidence, i.

3. Accurately aim the incident ray at X, and for each angle of incidence mark the directions

of the emergent ray with two crosses.

4. Remove the glass black, draw in the emergent and refracted rays and measure the angles

of refraction, r.

5. Tabulate the values of the angles of i and r and also the values of sin i and sin r.

12

6. Plot a graph of sin i against sin r.

The gradient of the graph will equal to the refractive index of the material.

Diagram showing the pathway of a ray of light through a glass block:

At X the incident ray 1 is bent or refracted as it enters the glass. At X, as the ray enters the

glass, angle r is smaller than angle i and we say the ray is bent towards the normal.

At Y, as the ray leaves the glass, it is bent back to its original direction. The angle of

refraction, now in the air, is larger than the incident ray.

When a ray of light enters an optically denser medium, it is bent towards the normal. When it

enters a less dense medium, it is bent away from the normal.

If the block of glass has parallel sides, the emergent ray, E, is parallel to the incident ray 1,

but it is laterally displaced.

13


A student was given an experiment to find the refractive index of glass as a CSEC Physics SBA

activity and produced the following results.

Angle of incidence,

i/degrees

Angle of refraction,

r/degrees

Sin i Sin r

10.0 6.0

20.0 12.0

30.0 18.0

40.0 24.0

50.0 30.0

60.0 36.0

(a) Complete the table above.

(b) Plot a graph of sin i against sin r.

(c) Find the slope, n, of the graph.

(d) What does the slope, n, of the graph represent?

_____________________________________________________________________________

(e) Draw a labelled diagram identifying the apparatus used and angles measured by the

student to obtain the results.

14

(f) A ray of light is incident at an angle of 350. With the aid of dotted lines, use your graph to

calculate the angle of refraction produced.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

15



TERM 3

PHYSICS

GRADE 10

WEEK 7 LESSON 2

TOPIC: Dispersion

The diagram below shows how a prism may be used to produce a spectrum from a source of

white light (sunlight).

Newton’s experiments laid the foundation for work on how colours are produced from white

light. He showed that while light could be split up into its constituent colours using a triangular

glass prism. The band of colours produced by the prism is known as the spectrum of light. The

separation of the colours by the prism is known as dispersion.

The importance of Newton’s prism experiment must be emphasized. While others had theorized

Newton experimented. He changed the hole size, varied the position of the prism with respect to

the hole used different thicknesses of glass in order to find out what caused the colour.

16

Finally, he placed a second prism as shown and found that on a screen placed beyond the prisms

a path of white light was formed.

Here was conclusive proof that white light is indeed composed of colours which are refracted by

the prism and not introduced or added by the prism.

In another experiment he produced a SINGLE COLOUR by putting a narrow slit in front of the

spectrum produced by a prism. He then passed this single colour through another prism. This

single colour was the only colour to be formed on the screen, showing that a single colour

produced by a prism could not be split into other colours.

17

The colours of the spectrum

The colours are in Newton’s prism experiments are those seen in a rainbow: red, orange, yellow,

green, blue, indigo and violet, in that order. The colours gradually change from one to the next

with no clear-cut boundaries between them. For this reason, the spectrum of white light

described as being continuous. Each colour has a different frequency and wavelength from the

others and the light (or visible) spectrum is in fact only a small part of a much larger spectrum

called the electromagnetic spectrum.

A mnemonic to remember the colours of the spectrum is ROY – G – BIV.

18


1 Define the term ‘dispersion’

______________________________________________________________________________

______________________________________________________________________________

2 With the aid of labelled diagrams, describe an activity to illustrate the phenomena of

dispersion of light

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

3 Draw labelled diagrams to show how the colours of the spectrum can combine to form

white light.

19



TERM 3

PHYSICS

GRADE 10

WEEK 7 LESSON 3

TOPIC: Critical angle and total internal reflection

When light goes from one medium in which it has low speed to a medium in which it has a

higher speed, its angel of REFRACTION is GREATER than its angle of incidence.

=

; if v2 > v1, θ2 > θ1

For each angle of incidence, the wave is BOTH REFLECTED (at an EQUAL angle) and

REFRACTED (at a GREATER angle).

At the CRITICAL angle of incidence, the wave is REFLECTED at the critical angle and

REFRACTED AT 900. (The refracted ray no longer passes into the second medium).

20

At any angle GREATER than the CRITICAL angle, TOTAL INTERNAL REFLECTION

occurs. (There is no refracted ray).

Conditions necessary for total internal reflection:

1. The ray of light is travelling from the more optically dense medium to the less optically

dense medium

2. The angle of incidence is greater than the critical angle

Problem solving:

The diagram above shows a ray of light, XY, incident on a right – angled prism, PQR, of

refractive index 1.5. The point of incidence on PR is such that the refracted ray inside the prism

is incident on PQ.

(i) Calculate the angle of refraction at the boundary, PR.

(ii) Given that the critical angle for the glass – air boundary, PQ, is 41.80, deduce whether or

not there would be total internal reflection at this boundary.

21

Solution:

(i) sin r =

r = sin-1 ( )

r = sin-1 (.

) = 28.10

(ii) At the PQ boundary, the ray will incident at an angle of 170. This angle is less than the

critical angle (41.80) so no total internal reflection will occur. Normal refraction will take

place.

22


1 Define the term critical angle

______________________________________________________________________________

______________________________________________________________________________

2 State the conditions necessary for total internal reflection

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

3 State three applications of total internal reflection.

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

23

4 The figure below is a side view of ABCD, a prism made from fused quartz (a type of

glass) of refractive index 1.46.

The ray MN is incident on face AD as shown.

Explain why MN will be totally internally reflected from the face AB.

24



TERM 3

PHYSICS

GRADE 10

WEEK 8 LESSON 1

TOPIC: Action of Lenses

A lens is any glass, plastic or other transparent refractive medium with two opposite faces, at

least one of which is curved.

Types of lenses

There are two basic types of lenses:

Converging lenses – are those that are thicker in the middle than at the edges and cause a

parallel beam of light to converge.

Diverging lenses – are thinner in the middle than at the edge and cause a parallel beam of light

to diverge.

25

Definitions relating to parts of a lens

The optical centre, C, is the point in the lens through which all rays will pass without any

deviation.

Object distance, image distance and focal length are measured from C.

The principal axis, XX’, is an imaginary line perpendicular to the lens and which runs through

the optical centre.

The principal focus, F, of a

i. converging lens is that point on the principal axis to which rays parallel to the principal

axis converge after refraction by the lens.

ii. diverging lens is that point on the principal axis from which a beam of light parallel to the

principal axis seems to come on leaving the lens.

The focal length, f, of a lens is the distance between the optical centre and the principal focus.

26

Since light can be incident on either side of a converging lens and a diverging lens, these lenses

would have two principal foci, one on either side of the lens.

The focal plane: this is the plane which is perpendicular to the principal axis and passes through

the principal focus.

27


1 In the space provided, draw a labelled diagram using the converging lens to show clearly

the following features:

i. Principal axis

ii. Principal focus

iii. Focal length

iv. Focal plane

2 Draw the ray shown as it emerges on the other side of the lens and its relation to the focus. Show the principal axis and the focal length.

28



TERM 3

PHYSICS

GRADE 10

WEEK 8 LESSON 2

TOPIC: Images by Lenses

Difference between real and virtual images formed by lenses

VIRTUAL IMAGE REAL IMAGE

Image is observed at the point from which

rays only seem to come, (but NO light rays

actually pass through this imaginary point of

intersection)

Image is formed where rays actually meet

No image is obtained on a screen placed at

this imaginary point (if it is possible to do so)

An image will be formed on a screen placed

at this point

Image is erect Image is inverted

Image is on the same side of the lens as the

object

Image and object are on opposite sides of the

lens

29

Examples of images formed by lenses

Virtual images produced by Real image focused on

A magnifying glass placed close to an object

(e.g. the print of a page)

Screen placed behind a magnifying glass set

in front of an open window

Spectacles used for correcting long and short

sightedness

Film of a camera

Retina of the eye (The image formed is real,

diminished and inverted)

Screen used with a projector (the image

formed is real, magnified and inverted

Procedure for drawing ray diagrams

The object and image are represented by arrows and real rays are represented as straight solid

lines with arrows indicating direction.

In order to determine the size and magnification of the image and whether it is erect or virtual,

we draw rays from the tip of the object which is positioned on the principal axis.

Images are formed where real rays come together or where rays seem to come from.

In the figure above, (a) is showing that a ray parallel to the principal axis is refracted (by the

lens) to pass through F.

In (b), a ray arriving through F is refracted parallel to the principal axis.

In (c), a ray of light through the optical centre is undeviated.

30


1 Define the term ‘real image’

______________________________________________________________________________

______________________________________________________________________________

2 Define the term ‘virtual image’

______________________________________________________________________________

______________________________________________________________________________

3 Complete the table below to compare real and virtual images. Use a for YES and X for

NO.

Real images Virtual Images

Image can be placed on a screen

Rays meet to form the image

Image is erect

Image is inverted

Image is on same side of lens as object

Image is on opposite side of the lens compared to

object

Image is produced by a magnifying glass

Image is produced by a projector

31



TERM 3

PHYSICS

GRADE 10

WEEK 8 LESSON 3

TOPIC: Ray diagrams

Placing the object between F and optical centre

Image formed is

1. virtual

2. erect

3. magnified

4. on the same side of the lens as the object and further away

Uses:

1. magnifying glass

2. instrument eyepieces

3. spectacles correction for long – sightedness

4.

32

Placing object at infinity

Image formed is at infinity.

Uses: produces a parallel beam of light as in a spotlight with lamp at O.

Placing object between F and 2F

Object formed is

1. real

2. inverted

3. magnified

4.

5. on opposite side of lens to O, beyond 2F

Uses:

1. projector

2. microscope objective lens

33

Placing object beyond 2F

Image formed is

1. real

2. inverted

3. diminished

4. on opposite side of lens between F and 2F

Uses:

1. camera

2. the eye

Object at infinity

Image formed is

1. real

2. inverted

3. diminished

4. on opposite side of lens at F

Uses: on objective lens of a telescope

34


Use graph paper and draw ray diagrams to get information to complete the table below.

Object height/

cm

Object distance/

cm

Focal length/

cm

Image height/

cm

Image

distance/ cm

5 7 10

5 15 10

5 22 10

35



TERM 3

PHYSICS

GRADE 10

WEEK 9 LESSON 1

TOPIC: Magnification

Linear magnification,m, is the factor by which the size of the object has been magnified by the

lens in a direction perpendicular to the axis of the lens.

It can be calculated by dividing the image height by the object height.

It can also be calculated by dividing the image distance by the object distance.

m =

=

m =

=

Magnification Effect of image when compared to the object

Greater than 1 Magnified

Less than 1 Diminished

Equal to 1 Same size

36


1 Keshorn investigated the relationship between image size, I, and object size, O, while

studying shadows.

His results are presented in the table below.

Image size, I/cm 2.5 5.0 7.6 10.0 12.6 15.0

Object size, O/cm 0.5 1.0 1.5 2.0 2.5 3.0

(a) Plot a graph of image size, I, versus object size, O.

(b) Calculate the gradient, G, of the line obtained.

(c) State the physical quantity with which the gradient of the graph, G, is associated.

______________________________________________________________________________

2 A 10 cm tall tablet computer was placed vertically 20 cm from a plane mirror. Its image

distance was found to be 20 cm.

Use the data given to calculate

(i) the height of the image of the computer

(ii) the magnification of this image

37



TERM 3

PHYSICS

GRADE 10

WEEK 9 LESSON 2

TOPIC: Focal length of a converging lens

The focal length, f, of a lens is related to the image distance, v, and the object distance, u, by the

following formula (lens formula):

= +

Practice problem:

An object is placed in front of a converging lens of focal length 12 cm. Find the nature and position of the image when the object distance is 16 cm.

Rearranging the formula, = –

= – =

v = 48 cm.

Image is real and 48 cm away from the optical centre.

38

Experiment to determine the focal length of a lens

Materials needed:

Converging lens

White screen

Metre rule

A distant object

Procedure

1. Hold the lens so that its axis points in the direction of the sun.

2. Place the screen behind the lens to receive light rays focused by the lens.

3. Move the lens and/or the screen along the axis of the lens until the sharpest image of the

Sun (or the distant object e.g. tree) is obtained on the screen as a tiny, brilliant spot of

light if the Sun is used, or a tiny tree or building, as the case may be.

4. Measure the distance between the centre of the lens and the screen at this point. Do not

forget that the lens does have some thickness.

5. Repeat the procedure from the beginning four more times.

6. Calculate the mean of the five readings taken.

Caution: Take care never to look directly at the Sun

39


1 The lens formula is = +

State what each symbol represent in the formula.

f:____________________________

u: ___________________________

v: ___________________________

2 Use the formula to complete the table below

u/cm v/cm f/cm

2.00 0.25

15.00 6.00

14.00 11.70

40



TERM 3

PHYSICS

GRADE 10

WEEK 9 LESSON 3

TOPIC: Problem solving: Focal length of a converging lens

In an experiment to determine the focal length of a convex lens, a group of Grade 11 students set

up the apparatus as shown below:

The students measured object distances (u) and corresponding image distances (v) and recorded

the information in the table below.

u/cm 𝟏

𝒖 ( ) v/cm 𝟏

𝒗 ( )

20.0 55.6

30.0 30.2

40.0 23.8

50.0 22.2

60.0 20.0

70.0 19.2

41

(a) Complete the table to show the values of and .

[Include units and calculate to three significant figures]

(b) Plot a graph of against .

(c) Calculate the gradient of the graph to one significant figure.

(d) State the value of the intercept, c, on the axis.

______________________________________________________________________________

(e) Given that c = , determine f, the focal length of the lens.

42



TERM 3

PHYSICS

GRADE 10

WEEK 10 LESSON 1

TOPIC: Problem solving: Refractive index

Testing of a new material to be used as an anti – reflective coating for eye glasses has yielded the

results shown below.

Angle of incidence, i/0 30.0 40.0 50.0 60.0 70.0

Angle of refraction, r/0 23.5 30.5 38.0 43.7 48.5

sin i

sin r

(a) Complete the table by calculating the values of sin i and sin r.

(b) Use the readings to plot a graph of sin i against sin r.

(c) Calculate the gradient of the graph

43

(d) Calculate the angle of refraction if the angle of incidence s 900 for this new material.

(e) The anti – reflective coating works best if its refractive index is the square root of the

refractive index is the square root of the refractive index of the lens in the eye glasses.

Determine the refractive index of the lens that gives the best result.

44



TERM 3

PHYSICS

GRADE 10

WEEK 10 LESSON 2

TOPIC: Problem solving

Electromagnetic waves consist of visible light and radiations higher or lower than the

wavelength of light.

(a) Identify ONE type of radiation with wavelength:

(i) longer than visible light _________________________________________

(ii) shorter than visible light _________________________________________

(b) Complete the table which relates to the sources and uses of electromagnetic waves

Name of wave Source Use

X – ray To take X – ray pictures

Gamma ray

Radio wave

(c) If gamma rays have a wavelength of 3.0 x 10-12 m, calculate the frequency of this type of radiation.

45

(Velocity of all electromagnetic waves = 3.0 x 108 ms-1)

(d) A ray of red light emerges from a glass block as shown below.

If the block has a refractive index of 1.5, determine the value of the angle e.

46



TERM 3

PHYSICS

GRADE 10

WEEK 10 LESSON 3

TOPIC: Problem solving

In 2010, Sound Navigation and Ranging (SONAR) was used to detect the presence of submerged

oil plumes in the Gulf of Mexico after a massive oil spill. The figure below shows a ship using

SONAR to locate an oil plume.

(a) Explain, with reference to the figure above, how SONAR was used to determine the

depth of an oil plume.

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

47

(b) If echoes are received 0.3 seconds after being sent, calculate the depth of the oil plume

below the detector, given that Velocity =

[Speed of sound in sea water = 1450 ms-1]

Types of Waves Pulses are di - Ministry of Education, Guyana

Documents

Transcript of Types of Waves Pulses are di - Ministry of Education, Guyana