s=ut+ at 21 -2 v 2=u 2+as

P=2l+2w

P= w -t

G R A D E B O O S T E RG R A D E B O O S T E R

I G C S E P H Y S I C SI G C S E P H Y S I C S

WAVES 3

EDEXCEL

Unit 3 Waves

作者 | Bettina Chan

出版 | Lab Edu Limited

版權為 Lab Edu Limited 所擁有

I GCSE PHYSICS - UNIT 3WAV ES

EdexcelIGCSE Physics Grade Booster

01 02

AFTER-CLASS EXERCISE

LESSON FLOW

1. PropertiesofWaves

2. TheElectromagneticSpectrum

3. LightWaves

4. Sound

1. Coverallkeypointsinthespecification

2. Gooversamplequestions

3. Masterexam-typequestions

CONTENT

P.03-06Properties of Waves

The Electromagnetic Spectrum

Light Waves

Sound

Unit 3 Questions

P.07-08

P.09-11

P.12-13

P.14-16

LEARNING OBJECTIVES

Question Type

1 Calculation

2 Calculation

3 Knowledge-based

4 Knowledge-based

5 Diagram

6 Calculation

7 Experimental

8 Calculation

9 Knowledge-based

10 Knowledge-based

03 04

Properties of WavesWavesareawayoftransferringenergyfromplacetoplace.

………………………….wave:

Particlemovementperpendiculartodirectionofwave.

………………………….wave:

Particlemovementparalleltodirectionofwave.

Describing Waves

………………………….: Themaximummovementofparticles fromthe resting

position/equilibriumposition

………………………….: Distancebetweenonecresttoanothercrest

Frequency:Thenumberofwavesproducedeachsecond,measuredinhertz(Hz)

f=………………………….(Hz)

T=………………………….(s)

E.g. Calculate the period of a wave with a frequency of 400Hz.

T=………………………….s

The wave equation

Wavespeed,v(m/s)=frequency,f(Hz)xwavelength,λ (m)

v=fxλ

v=………………………….(m/s)

f=………………………….(Hz)

λ=………………………….(m)

E.g.Ifawavetravelsat15m/s,andhasawavelengthof5m.Whatisthefrequency?

v=fxλ

………………………….=………………………….x5m

f= ………………………….Hz

vibrationofcoils directionofwave

vibrationofcoils directionofwave

wavelength

amplitu

de

1timeperiod,T(s)

Frequency,f(Hz)=

1T

f=

1f

T=

T=

05 06

Wavelength and frequency

*Highfrequency,shortwavelength*

*Lowfrequency,longwavelength*

Reflection

Theangleofincidence=Theangleofreflection

Refraction• Change/nochangeinwavedirection• Changeinwavespeed

Doppler effect

Whenanambulanceisstationary,thesoundwavespeoplereceivefromithavethe

samefrequencyandwavelength.

Whenanambulancemoves, thewavefrontsareno longerevenly spaced.The

wavesaheadofthecarwillbec…………………………asthecarismovinginthis

direction.Assuch,thewaveswillhaveas…………………………wavelengthand

ah…………………………frequency,thereforepersonhearingthesoundfromthe

frontofthecarwilllistensoundofah…………………………pitchandviceversa.

wavefrontsapproachthebarrier

angleofincidence

angleofreflection

normal

flatbarrier45º45º

directionofthewaveafterreflection

reflectedwavefronts

directionofwavefrontsbeforereflection

AMBULANCE

PersonA PersonB

07 08

The Electromagnetic SpectrumPropertiesofelectromagneticwaves:

1. Theyalltransfer…………………………

2. Theyareallt…………………………waves

3. Theyalltravelat…………………………m/sinavacuum

4. Theycanallber…………………………andr…………………………

R…………………………waves • Longestλ• Forcommunication

M…………………………• Forcommunication• Rader• Cooking

Cookingmethodofmicrowave:

1. Heatupwatermoleculesinfood

2. Veryhotwatermoleculescookfood

3. Therefore,thefoodiscookedthroughout

4. Notfromoutside

I…………………………• Allobjectsemitinfrared• Moreenergy=moreinfrared• Lowpenetratingpower• Above-273ºChaveinfrared• At-273ºCNoinfrared• Usedinremotecontrolsfortelevision,DVDplayers,specialcamerastosearchfor

peopleincollapsedbuildings/buildings

V…………………………light Usedinopticalfibres,communication,compactdiscsandbarcodes

U…………………………light • Damageskindependsondose Sunburn/blistering/skincancer/blindness

fluorescenttubesglow(shines)becausetheUVlighttheyproducestrikesaspecial

coating(covering)ontheinsideofthetube,whichthenemitsvisiblelight.

X-rays• Easilypass-throughbodytissue,canbeusedtocheckapatients’bones• Checkinternalstructuresofobjectslikebuildingsormachineries• Usedinairportsforsecuritycheckingprocedures• Causecancerdependsondose• Prevent:lead

G…………………………rays• Highpenetratingpower• Usedtosterilisemedicalinstrument• Higherenergythanx-rays• Treatcancer(killcancercells)butcanalsocausecancer• Prevent:lead

09 10

Light wavesLuminous:sun,lamp

Non-luminous:onlyreflectlight

Reflection

Whenalightrayisreflected,theincidentrayequalsthereflectedray.

Asarayentersaglassblock,its………………downandisrefracted………………the

normal.Astherayleavestheblockitspeedsupandisrefracteda………………………

fromthenormal.

Refractive index

Differentmaterialsbend light todifferentextentandthiscanbedescribedasa

refractiveindex.

Consideraglassblock,theangleofincidencewasmeasuredas35ºandtheangleof

refractionas20º,calculatetherefractiveindexoftheglassblock.

Investigate the refractive index for glass

1. Shinearayoflightontoaglassblock,sothattherayemergesontheoppositeside

oftheblock.Markthedirectionsofbothoftheserays.

2. Drawaroundtheglassblockbeforeremovingit.

3. Markthedirectionoftherayinwhichittravelledinsidetheglassblock.

4. Drawanormalatwheretherayenterstheblock.

5. Measuretheanglesofincidence(i) andrefraction(r) 6. Usetheequationtodeterminetherefractiveindexoftheglassblock.

Refraction

incidentray normal reflectedray

planemirror

i=angleofincidencer=angleofreflection

i r

incidentray

angleofincidence

normal

normallightisbentawayfromthenormal

lightisbenttowardsthenormal

air

air

glassangleofrefractionrefractedway

sinin=

sinr

sinin=

sinr

sin35n=

sin20

11 12

Total internal reflection

Theequationtodeterminetotalinternalreflectionisasbelow:

c=…………………………angle(incidence)

n=…………………………index

Application of total internal reflection: • Prismaticperiscope• Bicycleandreflection• Binoculars• Opticalfibre• Endoscope

iissmallerthancriticalangle

iisequaltothecriticalanglec

normalweakreflectedray

glass

air

angleofreflection

strongrefractedray

i r

weakreflectedray

glass

glass

air

c

i

c

i

refractedrayrunsalongtheboundary

strongreflectedray

Soundsareproducedbyobjectsthatarevibrating

Reflection

Shipsoftenuseechoestodiscoverthedepthofthewaterbeneaththem.Thisiscalled

echosounding.

1. Shipsemitsoundwavesandtheytraveltotheseabed.

2. Somewavesemittedarereflectedfromtheseabedbackuptotheship.

3. Equipmentontheshipdetectsthesesoundwaves.

4. Thetimeittakesthewavestomakethis journeyismeasuredtocalculatethe

depthofsea.

v=velocity

d=distance

t=timetaken

Refraction

Thesystemofusingechoesinthiswayiscalledsonar(Sound,NavigationandRanging).

1. Mostofthesoundweheartravelsinas…………………………line(PathB).

2. Butsometravelupwards(PathA).

3. Ifthetemperatureconditionsareright,soundwavesarer…………………………

andfollowacurvedpathdownwards(PathC).

4. Wecanthereforehavetwosetsofsoundwavesandthesoundwehearseems

louderandclearer.

Sound

IIII

IIIII

IIIIIIIIIIIIIIIIIIII

I I I I I I I I I I I I I I I I I I I I I

A:refractedsound waves

B:usualdirectpathofwavetolistener

listenersource

C:extrasoundwavesarriveduetorefraction

1sinc=

n

2dv=

t

13 14

Investigate the frequency of a sound wave using an oscilloscope

1. Connectamicroscopetoanoscilloscope.

2. Whenthesoundwaveentersthemicroscope,theoscilloscopedrawsalongitudinal

soundwaveasatransversewave.

Pitch and Frequency

Higherfrequency,…………………………pitch

Lowerfrequency,…………………………pitch

Loudness

Loudnessdependsontheamplitudeofawave.

1. Calculatethetimeperiodwhenthefrequencyis5000Hz.

2. Thewavelengthofasoundwaveis5m.Thesoundwavetravelsat344m/s.Calculate

thefrequencyofthesoundwave.

3.StatefourtwopropertiesofEMwaves.

4 (a). Suggestoneuseofmicrowaves.

(b).SuggestoneuseofX-rays.

(c). Suggestoneuseofgammarays.

5 (a). Angleof……………=Angleof……………

(b).

6. Angleofincidence=33º

Angleofrefraction=11º

Whatistherefractiveindex?

7. Describeproceduresastudentcancarryouttoinvestigatetherefractiveindexofa

glassblock.

8. Aboyclapshishandandhearsanechoafter0.4s.Thedistancebetweentheboy

andthewallis75m.Calculatethespeedofthesound.

9. Whatisthedefinitionoftransversewaveandlongitudinalwave?

10 (a). Asoundproducedbythehornofanapproachingcarisahigherfrequency.

Explain.

(b).Whatwillhappentothesoundheardbyanobserverifthecarismovingaway

atahighspeedcomparedtoastationarycar?

Unit 3 Questions

36º Xº

15 16

Mark scheme

1. f=1/t

t=1/f

t=1/5000

t=0.0002s

2. v=fλ

f=v/λ

f=344/5

f=68.8Hz

3. • Theyalltransferenergy.

• Theyallaretransversewaves.

• Theyalltravelat3x108atvacuum

• Theycanallbereflectedandrefracted

4 (a) Cooking

(b) Observingtheinternalstructureofobjectsandmaterial.

(c) Sterilisedfood

5 (a). Angleofincidence=Angleofreflection

(b).

X=36º

6. n=sini/sinr

n=sin33° /sin11°

n=2.85

7. • Usearayboxandarectangleglassbox

• Useaprotractortomeasuretheangleofincidence

• Obtainarangeofincidencevalue

• Plotagraphofsiniagainstsinr

• n=sini/sinr

• Findgradientofgraph

• Fixblockfirmlyinposition

8. v=s/t

v=75x2/0.4

v=375m/s

9. Longitudinalwave:Thevibrationoftheparticleisparalleltothedirectionofwave.

Transversewave:Thevibrationoftheparticleisperpendiculartothedirectionof

thewave.

10 a. DuetotheDopplereffect,thewavefrontsaresquashedclosertogetherasthe

carapproaches.

b. Thesoundwouldbelowerthanwhenthecarisnotmoving.36º Xº

s=ut+ at 21 -2 v 2=u 2+as

P=2l+2w

P= w -t

G R A D E B O O S T E RG R A D E B O O S T E R

I G C S E P H Y S I C SI G C S E P H Y S I C S

WAVES 3

EDEXCEL