NEET UG Physics Atom and Nucleus MCQs - Studiestoday

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Unit - 18Atom and Nucleus

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SUMMARY1 The distance of the closest approach of an - particle is given by

2

o K.

1 2Zeγo=4π E E where Ek= 21 m

2 9 Z = Atomic number

2. The Impact parameter is given by 2 θ

22

o

2Ze Cot1b = 4π.E m

3 No - of Scattering of - particle reattered at angle is given by

2

o 2 4Ζe 1N = N ns m sin θ/2

where, No = number of incident - particlesn = no. of Atoms per unit Volume in the foils = thickness of foilv = speed of - particle,m = mass of particlez = Atomic number of (the element of foil)e = charge of electron.

4 Angular momentum of electron in Bohr orbit

2nhmvr

, whre n is an integer

5 rn = radius of nth bohr orbit = 2 2

2

n h oZe m

rn

2nZ

6 Energy of electron in nth orbit is

4 2 2

n 2 2 22o

me z zE 13 . 6 evn n8h

2

n 2ZEn

7. different spetral Series Formula for and their gegionls

(i) Lyman series, 2 2

1 1 1R where, n 2,3....1 n

(ultra violet region.)



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ii) Balmer series, , 2 2

1 1 1R where, n 3, 42 n

,........

(Visible region.)

(iii) Paschen series, , 2 2

1 1 1R where, n 4,53 n

,........

(Infrared region.)

Braket series, 2 2

1 1 1R where, n 5, 64 n

,........

(Infrared region.)

Pfund series, 2 2

1 1 1R where, n 6, 75 n

,........

(Infrared region.)8 For, hydrogen atom energy of electron in nth orbit

n 2

13.6E eVn

For hydrogen like atom 2n 2

13.6E =- z eVn

9 A AZ ZX or X

Z = Atomic number = Number of ProtonsA = mass number = Number of neucleonsA - Z = N = Number of neutrons(i) For Isotope nuclei

Z equal and A unequale.g. 6c12 6c13

6c14

(ii) For, Isotone nucleiZ unequal, A unqualA-Z = N = equalNo - of neutrons are equal

e.g. 86 87kr Rb36 ,37(iii) For, Isobar nuclei

z unequal , A equal(A-Z) are unequale-g 12 12

5 6B , C



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(iv) For Isomers nuclerZ equal, A equalBut their radio active properies are different

e.g. 80

35Br pair

10 Radius of nucleus R = Ro (A) 13

Where Ro = Constant= 1.1 fm to 1.2 fm

A = mass number11 Mass defect MNmnzmm p )(

12 B.E 2 2bE ( m)c Zmp Nmn) M c

13 Unit of energy in nuclear Physics or atomic Physics is eV191eV 1.6 10 J

14 unit of mass in nuclear physics or atomic Physics is amu or u271amu 1u 1.67 10 Kg

61u 931.48MeV 931.48 10 eV

15 B.E Per nucleon is n

bb

EEA

16 - Particle = Nucleus of Helium atomSymbol of - Particle 4

2 He

- Paricle = electron emitted From nucleus ieo

γ - radiation = photon. Symbol γ

- particle or e1 or electron Particle or e1 or positron.

n p + e

n e

Where Anti neutrino neutrino

(17) unit of Radio activity1 Bq = 1 disinteglation/s1 curie = 3.7 1010 disinteglation/s



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(18) Activity dnI Ndt

number of Atoms or nucler in a Radio active sample after time is given bytN No e Where is radio active decay Constant

Activity I = tIo e

Mass tm mo e

(19) Half life 12

0.693T

Mean life T 1 12

T 0.693T Or 12T 1.44 T

(20) In - deccay Z decreasc by 2 and mass number A decrease by 4 In β - deccay Z increase by 1 and mass number does not change

In deccay Z decrease by 1 and mass number does not change In emission of r - ray or photon, Z and A does not change.

(21) Nuclear Fission.The spiliting of a heavy nucleus into two or more fragments or moderate andcomparable sizes is called nuclear Fission

e.g 235 141 92 1q2 56 36 OU Ba Kr 3 n energy

(22) Nuclear fusion.The Process of nuclear fusion consists in the combination of two light nuclei toform steble nucleus of mass less than the total intial mass.1 1 21 1 1

1 2 31 1 23 3 4 1 12 2 2 1 1

H H H e

H H He

He He He H H

If any Q > 0 Exoergic Q < 0 EndoergicIn any nuclear reactions consveration of momentum, charge and energy is must.

(23) Nucler reaction A (a,b) B or A+a B + b + QA = Target Nucleusa = Projected ParticleB = resulting (product) nucleusb = emitted ParticleQ = energy equal muss defect



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MCQFor the answer of the following questions choose the correct alternative from

among the given ones.

(1) In each of the following question match column -I and column -II select correctAnswer.(A) Bohr atom model (P) fixed for the atom(B) Ionisation potential (q) Nucleus(C) Rutherford atom modal (r) stationary orbits(D) Thomson atom modal (s) In atom positive and Nagative

charge are distrited uniformely.(A) as , br , cq , dp(B) ar , bp , cq , ds(C) ap , br , cs , dq(D) bp , cq , br , ds

(2) Read the following question and choose correct Answer form given below.(A) Both assertion and reason are true. Reason is the correct explanation of theAssertion(B) BOth assertion and reason are true. Reason is not correct explanation of theassertion(C) Assertion is true but reason is false.(D) Both Assertion and Reason are false(i) Assertion :- In a radio-active disintegration, an election is emitted by nucleus.Reason :- eleccon are always Present in-side the nucleus.(ii) Assertion :- An election and Positon can annibilate each other creating PhotonReason:- Electon and Positon form a Particle and anti Particle.(iii) Assetion:- An isolated radioactive atom may not decay at all what eVer be itshalf timeReason:- Readioactive decay is a statistical Phenomena.(iv) Assertion :- Fragment Produced in the fission of u235 are activeReason:- The fragments have abnormally high Proton to neutron ratio

(3) Each of the following question contain two stalements.choose correct answerform the given below.(i) statement-I:- Large angle scattering of al-pha Particle led to discovery ofatomic nucleus.



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state ment-II :- Entire Positive charge of atom is concentrated in the central core.(A) statement -I and II are true. and statement II is correct explanation ofstatement-I(B) statement -I and II are true, but statement-II is not correct explanation ofstatement I(C) statement I is true, but state ment II is false.(D) statement I is false but statement II is true(ii) statement-I 1 amu=931.48 MeV statement-II It follows form E=mc2

(iii) statement -I:-half life time of tritium is 12.5 yearsstatement-II :- The fraction of tritium that remains after 50 years is 6.25%(iv) statement-I:- Nuclei of different atoms have same sizestate ment-I I :- R =Ro(A)1/3

(4) Match column I and II and chose correct Answer form the given below.(a) Nuclear fusion (p) converts some matter into energy(b) Nuclear fission (q) generally Possible for muelei low atomic number(c) decay (r) generally Possible for ndcler high atomic number(d) Exothermic nuclear (s) Eessentially Proceeds by weak nuclear for(c) reaction(A) ap , br , cd , dq(B) ad , br , cp , da(C) aq , br , cd , dp(D) ar , ba , cp , da

(5) A radioative sample has no active atom at t=o, at the rate of dissntegration at any

time is R and the number of atom is N, then ratio.RN

varies with time (t) as.

(A)

t

RN

(B)

t

RN

(C)

t

RN

(D)

t

RN



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(6) The transition the state n=4 to n=1 in a hydrogen like atom results in ultravioletradiation. Infrared radition will be obtained in the transition form(A) 32 (B) 5 4 (C)42 (D) 21

(7) In Bohr model the hydogen atom, the lowest orbil corresponds to(A) Intinite energy (B) zero energy(C) The minimum energy (D) The maximum energy

(8) Energy leVels A , B , C of a certain atom corresponding values of energy i.eA B cE E E If 1 2 3, , are wave lengths of radition corresponding to the

transition CB , BA and CA. which of the following is correct(A) 2 2 2

3 1 2 (B) 3 1 2

(C) 1 23

1 2

(D) 1 2 3 o

(9) According to Bohr's theory the radius of electon in an orbit described by Principalquantum number n and atomic number Z, is Proportional to.

(A) 2 2Z n (B) 2n

Z(C)

2Zn

(D) 2

2

nz

(10) The energy of electron in the nth orbit of hydogen atom is expressed as

n 2

13.6E evn

The shortest and longest wave length of lyman series will be.

(A) o o910A , 1213A (B) 1315A ,1530 A

(C) 5463A ,7858A (D) None of these(11) Number of spectral lines in hydrogen atom is.

(A) 6 (B) 8 (C) 15 (D) (12) In the nuclear reaction 7

3X ( , ) Li the atom X will be

(A) 42 He (B) 11

5 B (C) 105 B (D) 9

5 B

(13) The nucleus which has radius one third of the radius of 189Cs is(A) 9Be (B) 19F (C) 12C (D) 7Li

(14) A nucleus of 210

84 Po originally at rest emits -particle with speed v what will be

the recoil speed of the daughter nucleus

(A) 214 (B) 4

214 (C) 4

206 (D) 206



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(15) It the radius of a nucleus of mass number 3 is R. then the radius of a nucieus ofmass mumber 81 is

(A) 27 R (B) 9 R (C) 3 R (D) 1227 R

(16) The nucler of which of following Pairs of nuclei are isotones

(A) 74 7134 31Se , Ca (B) 92 92

42 40Mo , Zr

(C) 81 8638 38Sr , Sr (D) 40 32

20 16Cd , S

(17) An electron change its Position from orbit n=4 to the orbit n=2 of an atom thewave length of emitted radition in the form of R (where R is Redburg constanst)

(A) 167R (B) 16

R (C) 163R (D) 16

5R

(18) The control rod in a nuclear reactor is made of(A) uranium (B) Cadmium (C) plutomium (D) grabhite

(19) which of the following isotopes normally fissonable

(A) 23392 U (B) 238

92 U (C) 23592 U (D) 239

93 Np

(20) which of the following statement is true

(A) 19278 Pt has 78 neutrons (B) 234 234 4

90 91 2Th Pa He

(C) 238 234 492 90 2U Th He (D) 84

214 21082Po Pb

(21) A Free neutron decays into a Proton, an electron and(A) (B) (C) (D)

(22) The distance of the closest abbroach of an alpha particle fired at a nuclous withkinctic energy K is ro. The distemce of the closest approach when thw -particle is fired at the same nucleus with kinetic energy 2k will be.

(A) or2 (B) 4ro (C) or

4 (D) 2ro

(23) which of the following series in the spectrum of hydrogen alon lies in the visiblelegion of the electro magnetic spectrum?(A) Paschen (B) Lyman (C) Brakett (D) Balmer

(24) If 13.6 eV energy is required to ionige the hydrogen aton the energy required toremove the electron form n=2 state is(A) Zero (B) 10.2 eV (C) 6.8 eV (D) 3.4 eV



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(25) It No is the original mass of the substance of halt lift 5 years, the amount ofsubstance left after 15 years is

(A) oN16 (B) oN

8 (C) oN4 (D) oN

2(26) when u-238 nucleus originalluy at lest decay by emitting an -particle having a

speed u the recoil speed of the resi-dual nucleus is.

(A) 4u238 (B) 4u

238 (C) 4u

234 (D) 4u234

(27) At a certain instant, a radioactive sample has a decay rate of 5000 dis-interationPer minute. After 5 minuter the decay rate is 1250 dis-interations Per minute.Then the decay constant is (Per-min )(A) 0.2 ln 4 (B) 0.4 ln 4 (C) 0.4 ln 2 (D) 0.8 ln 2

(28) A nucleus with Z=92 emits the following sequence, , , , , , , , , , , , , The Z of the resulting nucleus is

(A) 76 (B) 78 (C)74 (D) 82(29) which of the following can not be emitted in radioactive decay of the substance?

(A) Helium-nucleus (B) Electrons (C) Neutrions (D) Proton.

(30) It the radius of 27

13Al nucleus is 3.6 fm the radius of

125

52Te nucleus is nearly equal to

(A) 8 fm (B) 6 fm (C) 4 fm (D) 5 fm(31) which of the following atom has the lowest ionization potentical?

(A) 14

7N (B)

40

18Ar (C)

133

55cs (D)

16

8O

(32) If the binding energy of electron in a hydrogen atom is 13.6 eV, the energyrequired to remove the elecron form the first state of Li2+ is.(A) 13.6 eV (B) 30.6 eV (C) 122.4 eV (D) 3.4 eV

(33) The ionigation Potential of hydrogen atom is 13.6 eV. An electron in the groundstate absords Photon of energy 12.75 eV. How many dirrerent spectral lines canone expect when electron make a down ward transition(A) 1 (B) 2 (C) 6 (D) 4

(34) A radio-active nucleus AZ X emits 3 -particles and 2 Positrions. the ratio of

number of neuleuons to that of Protons in the final nucleus will be

(A) A Z 8Z 4

(B) A Z 12Z 4

(C) A Z 4Z 8

(D) A Z 4Z 2



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(35) An -particle of energy 21 mv2 bombards by a heavy nuclear target of charge ze.Then

the distance of closet approach for the alpha nucleus will be Probprtional to

(A) 3

1Z (B) 4

1

(C) 1m (D) 2

1

(36) when 7

3Li nucler are bombarded by Proton and the resultant nuclei are

8

4Be , the

emitted particle will be(A) neutron (B) gamma (C) alpha (D) Beta

(37) starting with a samble of Puer cu-66, 78 of it decays into Zn, 15 minules the left

of the samble is(A) 5 min (B) 7.5 min (C) 10 min (D) 15 min

(38) An -particle of energy 5 MeV is scattered though 180 by a fixed uraniumnucleus. The distance of the closest approach nucleus The distance of the closestapproach is of the order of(A) 810 cm (B) 1210 cm (C) 1010 cm (D) 1510 cm

(39) The binding energy Per nucleon of deutron 21 H and Lielium nucleus 4

2 H e is1.1 MeV and 7.0 MeV.resbectively. If two beutron nucler react to form a singlehelium nucleus, the energy released is(A)23.6 MeV (B) 26.9 MeV (C) 13.9 MeV (D) 19.2 MeV

(40) The nucleus at rest disintegrate into two nuclear parts which have their velocitiesin the ratio 2:1 The ratio of their nuclar sizes will be(A) 3 2 :1 (B) 1:3 2 (C) 3 :1 (D) 1: 3

(41) A radiation of energy E falls normally on a Pertect reflecting surface. Themomentum transterred to the surtace is.(A) E

c (B) 2Ec (C) 2

Ec (D) Ec

(42) In the following nuclear fusion reaction2 3 4 11 1 2 oH H He n

the repalsive potential energy between the two fusing nucler is 147.7 10 J TheTemperature to which the gas must be heated is nearly (Boltzman constmtK= 23 11.38 10 JK )(A) 310 K (B) 510 K (C) 710 K (D) 910 K



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(43) 9 If the binding energy Per nucleon in 73Li and 4

2 He nucler is 5.6 NeV and 7.06

MeV respectively, then in the reaction 4

3 2P Li 2 He

(P here retrent Proton)

enery of Protpn must be(A) 1.46 MeV (B) 39.2 MeV (C) 17.28 MeV (D) 39.2 MeV

(44) 9 f mo is the mass of an isotope 178 0 , mp and mn are the masses of a Proton and

neutron respectively, the binding energy of the isotebe is

(A) 2o p(m 8m )c (B) 2

o p n(m 8m 9m )C

(C) 2o n(m 17m )c (D) 2

om c

(45) In gamma ray emission form a nucleus(A) there is no change in the proton-number and neutron number(B) Both the number are changes(C) only Proton number change(D) only neutron number change

(46) The half life time of a radidactive elements of x is the same as the mean life ofanother radioactive element Y. Initially they have same number of atoms, then(A) y will decay faster thean x(B) x will decay faster then y(C) x and y will decay at the same rate at all time(D) x and y will decay at the same rate intially.

(47) which of the following transition in hydrogen atoms emits Photon of highestfrequengy?(A) n=2 to n=6 (B) n=1 to n=2

(C) n=2 to n=1 (D) n=6 to n=2

(48) An electron Passing through a Potential diffencne of 4.9 v colides with a mercuryatom and trnasfer it to the first excited state what is trnasfer it to the first excitedstate. what is the wave length of Photon corresponding to the franition ofmercury atom to its normal state.

(A) 2050 A (B) 2935A (C) 2525A (D) 2240 A



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(49) The binding energy Per nucleon for the Parent nucleus is 1E and that for the

daughter nuclei is 2E then

(A) 1 2E E (B) 1 2E E (C) 1 2E E (D) 1 2E 2E

(50) The speed of daughter nuclei is

(A) m cM m

(B) mCm (C) 2( m)C

M (D) mC

M m

(51) Light form the discharge tube containing hydrogen atom falls on the surface of aPiece of sodium. The kinetic energy of the fastest photo electrons emitted formsodium is 0.73 eV. The work function for sodium is 1.82 eV. Ionigation Potentialof hydrogen is 13.6 v and the mass of hydrogen atom is 271.67 10 kg.

(i) The energy of Photon causing the Photo electeic emission is(A) 194.08 10 J (B) 192.912 10 J

(C) 191.744 10 J (D) 191.168 10 J

(ii) The quantum number of the two leVels in the emission of the Photons are(A ) n=1 , n=3 (B) n=2 , n=4 (C) n=1 , n=4 (D) n=3 , n=4

(iv) In this transition change in the angular momentum of electron is (where h isPlank constanst )

(A) h2 (B) h

(C) 2h

(D) 3h

2

(v) The recoil speed of emitting atom caussing that is at lest before the transitionis of the order of

(A) 11 cms (B) 2 110 ms (C) 4 110 ms (D) 11ms

(52) A and B are two radioactive substane whose half lives are 1 and 2 yearsrespectively. Initially 10 g of A and 1 g of B is taken. The time after which theywill have same quantity remaining is(A) 3.6 years (B) 7 years (C) 6.6 years (D) 5 years

(53) which of these is a fusion reuction

(A) 3 2 4 11 1 2 0H H He n (B) 12 12

7 6C C g

(C) 238 206 4

92 82 2 1U Pb 8 He 6 e

(D) None of these



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(54) The activity of a sample of a radioactive material is at time t1 and A2 at time t2

(where t2>t1) if T its mean life is then

(A) 1 1 2 2A t A t (B) 1 2(t t )T2 1A A e

(C) 1 2 2 1A A t t (D) t1 Tt2

2 1A A e

(55) In the following disinteglation series238 A

92 ZU x y

The value of Z and A respectively will be(A) 90 , 234 (B) 92 , 236 (C) 88 , 234 (D) 91 , 234

(56) gf 23892 U undergoes sucesively 8 decays and 6 decays then resulting nucleus is

(A) 206Pb (B) 208Pb (C) 214Pb (D) None of thes(57) The energy released by the fission of one unanium atom is 200 MeV. The number of

fission Per second required to Produce 3.2 w of Power is(A) 1010 (B) 710 (C) 1210 (D) 1710

(58) Radio carbon dating is done by estimating in the specimen(A) the amount of oridinary carbon still present

(B) the radio of the amounts of 14 126 6C C

(C) the amount of radio carbon still Present(D) None of these

(59) The enery difference between the first two leVels of hydrogen atom is 10.2 eV. whatis the corresponding energy difference for a singly ioniged helium atom?(A) 10.2 eV (B) 81.6 eV (C) 20.4 eV (D) 40.8 eV

(60) The total energy of the elcton in the first excited state of hydrogen is -3.4 eV. what isthe kinatic energy of the electron in this state?(A) 6.8 eV (B) 3.4 eV (C) -3.4 eV (D) -6.8 eV

(61) The wave length of second line of Balmer series is 486.4 nm. what is the wave lengthof the first line of lyman saries ?(A) 364.8 nm (B) 729.6 nm (C) 121.6 nm (D) None of these

(62) The innermost orbit of the hydrogen atom has a radius 0.53 A. what is radius of 2nd

orbit is ?

(A) 2.12A (B) 1.06A (C) 21.2A (D) 10.6A



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(63) If a hydrogen atom emits a Photon of wave length, the recoil speed of the atom ofmass m is given by

(A) mh

(B) mh

(C) mhλ (D) mh

(64) A freshly PrePared radio active source of half time 2 h emits raditation of intenisitywhich is 64 times the Permissible safe leVel. The minimum time after which is wouldbe possible to work safely with this source is.(A) 6 h (B) 24 h (C) 12 h (D) 36 h

(65) I n R uthertord experiment, the numer of Particles sccttered at 90o angle are 28 Permin. then the number of Particles at the angle 1200 in Per min will be(A) 25 (B) 12.0 (C) 50 (D) 112

(66) The Rutherford reVolution Per second made by an electron in the first Bohr orbit ofhychogen atom is of the order of(A) 1510 (B) 2010 (C) 1010 (D) 1910

(67) The half time of a radioafive substance is 20 min, difference between Points of timewhen it is 33% disintegeated and 67% dissintenated is aPProximately(A) 10 min (B) 20 min (C) 40 min (D) 30 min

(68) The size of the atom is of the order of(A) 1410 m (B) 1010 m (C) 810 m (D) 610 m

(69) The size of the nucleus is of the order of(A) 1010 m (B) 1410 m (C) 1910 m (D) 310 m

(70) The ratio of atomic volume of nuclear volume is of the order of(A) 1510 (B) 1010 (C) 1510 (D) 1010

(71) Nucleon is common name for(A) electron and neutron (B) Proton and neutron(C) neutron and Positron (D) neufrom and neurtino

(72) The nucler 147 N and 13

6C can be desribed as

(A) Isotones (B) Isobars (C) Isotope (D) Isomer(73) Plutoniumdecays with half life time 24000 yer. if Plutonium is stored after 72000 yes,

the fraction of it that remain

(A) 12 (B) 1

9 (C) 112 (D) 1

8



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(74) The radio of minimum to maximum wave length in Balmer series is

(A) 14 (B) 5

36 (C) 34 (D) 5

9(75) If the binding energy of electron in a hydrogen atom is 13.6 eV , the energy required

to remove the electron f rom the second exci ted state of L i ++ is(A) 13.6 eV (B) 3.4 eV (C) 30.6 eV (D) 122.4 eV

(76) A radioactive substance decays to 116 th of its initial activity in 40 days. the half life

of the radioactive substance expressed in day is(A) 20 (B) 5 (C) 10 (D) 4

(77) Complete the reaction 1 235 144 1o 92 56 on U Ba 3 n

(A) 9036 Kr (B) 89

36 Kr (C) 9136 Kr (D) 92

36 Kr

(78) 126C absorbs an energetic neutron and emits a β Partical. The resulting nucleus is

(A) 137 N (B) 14

7 N (C) 136C (D) 12

6C

(79) two deutrons each of mass m fuse to form helium resulting in release of energy Ethe mass of helium formed is

(A) 2

Emc

(B) 2

Emc (C) 2

E2mc

(D) 2

E2 mC

(80) what Percent of original radio active substans is left after 5 half life time(A) 3 % (B) 5 % (C) 6% (D) 12 %

(81) In which region of eletromagnetic spectum does the Lyman series of hydrogenatom like(A) x-ray (B) Intrared (C) visible (D) ultraviolet

(82) In terms of Rydergi constent R. The wave number of first Balmer line is

(A) 5R36 (B) 8R

9 (C) R (D) 8R20

(83) The hydrogen atom can give specral lines in the series Lyman, Balmer and Paschen.which of the following statement is correct(A) Lyman series is in the intrared region(B) Balmer series is in the ultravioet region(C) Balmer series is in the visible region(D) Paschen series is in the visible region.



301

(84) The ionigation energy of hydrogen atom is 13.6 eV. The ionigation energy of heliumatom would be(A) 27.2 eV (B) 13.6 eV (C) 54.4 eV (D) 6.8 eV

(85) A gamma ray Photon creates an electon- Positon Pair. If the rest mass energy of anelectron is 0.5 MeV. and the total kinetrc energy 0.7 MeV, then the energy of thegamma ray Photon must be(A) 3.9 MeV (B) 1.78 MeV (C) 0.78 MeV (D) 0.16 MeV

(86) The masses of netron and Proton are 1.0087 amu and 1.0073 amu respectively. It theneufron and Protons combins to form binding energy of the helium nucleus will be(A) 14.2 MeV (B) 28.4 MeV (C) 27.3 MeV (D) 20.8 MeV

(87) Large angle scattering of - particle could not be explained by(A) Thomson modal(B) Ruther Rutherford and Thpmoson modal(C) Both rutherford and Thomoson modal(D) Neither Ruthorford modal norThomson modal

(88) T he energy of an eleforn in nth orbit of hychogen is 2

13.6n

eV. energy required to

exite the electron form the first orbit 4th orbit is(A) 13.6 (B)3.4 eV (C) 0.85 eV (D) 1.5 eV

(89) The activity of a radioactive sample is measured as no conuts Per minute at t=o andNo counts Per minute t=5 min The time (in min) at which activity reduces to half itsvalus is

(A) 2log e5 (B) 105log 2 (C) e5log 2 (D) 2

510log

(90) A heavy nuecleus at lest breaks into two frigments which fly off with velocities inthe ratio 8:1 The ratio of radil of the frigments is(A) 1:2 (B) 4:1 (C)1:4 (D) 2:1

(91) The binding energy Per nucleon of 168O is 7.97 MeV and that of 17

8O is 7.75 MeV

The energy (in-MeV) required to remove a neutrom from 178O is

(A) 3.65 (B) 7.86 (C) 3.52 (D) 4.23

(92) The shape of the graph lnI t is(A) stright Line (B) Parabolic curve(C) Hyberbole curve (D) random shabe curve



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(93) The fig shows an energy leVes for the electron in a certain aton which transition in arepresents the emission of a Photon with most energy?

n = 4n = 3

n = 2n = 1I II IIIIV

(A) III (B) Iv (C)I (D) II(94) The Probability of survival of a radioactive nucleus for one mean life time is

(A) 11e

s (B) 1e (C) 2

e (D) 3e

(95) A s the electron in B ohr is orbi t of hydrogen atom Passes f rom state n=2 to n=1, theK.E. and Potential energy changes as(A) Two fold , also two fold(B) four fold , two fold(C) four fold , also four fold(D) two fold , four fold

(96) In the nuclear decay below A A A 4 A 4Z Z 1 Z 1 Z 1X Y B B

(A) , , (B) , , (C) , , (D) , ,

(97) The wave lenght of the first line of Lyman series for hydrogen atom is equal to thatof hydrogen atom is equal to that of second line of Balmar series for a hydrogen likeion. The atomic number Z of hydrogen like ion is(A) 1 (B) 2 (C) 3 (D) 4

(98) A nucleus mn x emist one -Particle and two Particle. The resulting nucleus is

(A) m 4n 2Y

(B) m 6

nY (C) m 4

nY (D) m 6

n 4Y

(99) Af a certain time, a radio active sample contains 202 10 atoms and disintegrationrate is 103 10 atom persec. when 152 10 atoms are Left to decay its disintegationrate will be(A) 53 10 atom / s (B) 103 10 atom/s

(C) 16.6 10 atom / s (D) 22.0 10 atom / s



303

(100) excited hydrogen atom emits a Photon of wave lenght in returninr to the groundstate The quantum number n of exilted state is given by

(A) R 1R

(B) RR 1

(C) R(R 1) (D) R(R 1)

(101) The radius of Ge nuclide is measured to be twice the radius of 94 Be . The number of

nucleons in Ge are

(A) 72 (B) 78 (C)65 (D)80

(102)Match column I and II

column I column II

(a) sige of nucleus (P) Z

(b) number of Proton in (q) 1510 m

a nucleus (r) (A-Z)

(c) size of Atom (s) 1010 m

(d) Number of nentrous in a nucles

(A) ar, bs, cq, dp

(B) aq, bp, cs, dr

(C) as, br, cq , dp

(D) bs, cp, cq , dr



304

KEY NOTE1 26 A 51 (i) A 73 D 98 C2 27 A (ii) B 74 D 99 A3 28 B (iii) B 75 A 100 B4 29 D (iv) D 76 C 101 A5 A 31 C 52 C 77 B 102 B6 B 30 B 53 A 78 A7 C 32 B 54 B 79 C8 C 33 C 55 D 80 A9 B 34 C 56 A 81 D10 A 35 C 57 D 82 A11 D 36 B 58 C 83 C12 D 37 A 59 D 84 C13 D 38 B 60 B 85 B14 C 39 A 61 C 86 B 15 C 40 B 62 A 87 A16 A 41 B 63 A 88 C17 C 42 D 64 B 89 C18 B 43 C 65 B 90 A19 C 44 B 66 A 91 D20 C 45 A 67 B 92 A21 B 46 A 68 B 93 D22 A 47 C 69 B 94 B23 D 48 C 70 C 95 C24 D 49 A 71 B 96 A25 B 50 C 72 A 97 B

(B) ar, bp, cq, ds(i) c (ii) b (iii) a (iv) d(i) a (ii) b (iii) c (iv) d(C) aq, br, cs, dp



305

Hints(1) Bohr atom model stationary Orbits

Ionization Potential Fixed for the atom Rutherford atom model Nucleus Thomson atom model In atom positive and Negative charge are distaibuteduniformly.

(4) Nuclear fusion generally Possible for nuclei low atomic number Nuclear fission generally Possible for nuclei high atomic number - decay Eessentially Prcoceeds by weak nuclear forces. Exothermic nuclear reaction Convets some matter into onergy..

(5) disintegration rate NdtdN

R N RN

Constant

the graph of R tN

will be steaight line.

(6) 54 transition series of paschen which is fall in infrared region(7) Ans (C) The minimum energy

Orbit energy ev6.13)1(

6.13n

6.13E 22n

(8) Ans (C) fig From 3hc

2hc

1hc

A1

A2A3

31

21

11

21

213

(9) Bohr radius r = 2 2

2

n h oe m

2nr

Z



306

(10) For, shortest wave length in Lyman series

2 2

1 1 1R min 911Amin 1

For, longest wave rength in Lyman series

max2 2

1 1 1R 1215Amax 1 2

(11)(12) 7

3X (n , ) Li

A 1 7 4Z o 3 2X n Li He By equating Z and A we getA 10Z 5X B

(13)1

32 oR R ( A )

(14) According to conservation of momentum

1 1 2 2

1 2

2 1

12

m v m v o4v 206 v o

206 v 4v4v v

206

Recoil speed of daughter nucleus is

4v206

(15) 13

oR R (3) 11 30R R (81)

11 3 13R 81 (27) 3

R 3

1R 3R

(16) Isotones nucler have same neutronsi.e. A-Z are equal.

74 7134 31From thegiven pairs se , Ca

has same neutruns



307

(17) 2 2

1 1 1Rm n

(18)(19)

(20) 238 234 492 90 2U Th + He

(21) n p e

P n e

(22) At a distance of closest approach kinetic energy of - particle = Potenticalcnergy of the system

2 1 21

Kq q1 mv K2 ro

1 2

1

Kq qroK

When kinetic energy 219 than

1 roo2

r

(23)

(24) Inigation potentier (For hydrogen) n 213.6E = eVn

(25) 12

tTN 1

2no

(26) According to conservation of momentum(27) t t

o oN N e I I e

1250=5000 5e

51 e4

54 e

n4 5 l

1 n4 0.2 n45



308

(28) Atomic number of final nucleus

= 92 -2 (no.of - Particle) + 1 (No. of Particle)

- 1(No.of Particle)

= 92 - 2 8 + 1 4 - 1 2= 78

(29)

(30) use formula 13R= Ro (A)

(31) 13355Cs a mucleus having highest Z number, the outer most electron are less in

binding with nuclera. That meam lowest binding energy.

(32) Binding energy 2

2

13.6zn

For Li2+ Z = 3, n = 2 first exited state

(33) n 1E E E

n 1E E E 12.75 13.6 0.85

n 2

13.6En

2

13.60.85n

2 13.6n 160.85

n 4

(34) 3 2eA A 12 1 A 12Z Z 6 Z 8X X Y

Number of newfrons = (A 12) (Z 8)

A 12 Z 8

=A - Z - 4

Number of protom Z 8

No.of neutrons A Z 4No.of Pr otons Z 8



309

(35) at distance of closest approach K.E = P.E2

22

1 1 (ze)(ze) zemv ro2 4 ro mv

1ro m

(36)

(37) 12

N 1 t where nNo 2 T

(38)(39) 2 2 4

1 1 2H H He

B. E of Helium = 4(7)-[2(1.1)+2(1.1)]= 28-4.4= 23.6 eV

energy relewed is 23.6 eV(40) According to cosveration momentum

m1v1= m2v2

1 2

2 1

m v 1m v 2

31

32

r 12r

131

2

r 1r 3

r1 : r2 = 1 : 3 2

(41) Here, surface is perfacet reflector momentum of incident radiation is E/C

momentum of reflected rediation is - E/C change in momentum = - cE c

E =

2EC

Momentum transtered to the surface = 2EC



310

(42) 3E KT2

(43) Energy of proton ( 11H ) = 4 (7.06)2 7(5.6)

= 2 28.24 39.2 = 2.3948.56 = 28.17

(44) Ans (B) 2 2B.E mc mo 8mp 9mn C

(45)

(46) 0.6931T 2 x

Y

1Ty

1 y

2

T Tx

0.693 1yx

dxy

0.693

12 X

T T y

y 1.44 x

y1

x693.0

According tN Noe

(47) n = 2 to n = 6 absorbs photonn = 9 to n = 2 absorbs photonn = 6 to n = 2 emission of photonn = 2 to n = 1 emission of photon

2 113.6 13.6E E E 0.38 13.6 3.02eV.36 4

12 1

13.6 13.6E E 3.4 13.6 10.2ev.4 1

1 E

hf ' hf(48) energy of electron = ve

19E 4.9 1.6 10 .J

hc hcE



311

(49)

(50) 22 CmMv21

22 2 m C

VM

2( m)V Cm

(51) (i) Kmax = hf - φ

hf = Kmux + φ

(ii) Correspnding energy leVel for 2.55 eV is n = 2 , n = 4Ans (B)

(iii) Change Angular momentum = 4h 2h 2h h h2 2

Ans (B)(iv) Accoding to conservation of momentum

momentum of photon = momentum of lecoil altom.

h mu

h hf Emcm mc

v

(52)

tT1

2 t11

t1

m 1 1 1mb 2 2 2

110m2

1 2m m

2 t2

1m2

tt2

10 12 2

t210 (2)

tlog10 log 22

3010.02t0000.1

64.6t year 6.6 year



312

(53) Ans (A) 3 2 4 11 1 2 0H H He n

(54) 1tt

1 0A A ete t t

o 0A A A A e

10

1

AA te T

1tT

0 1A A e

Now, 2tT

2 0A A e

1 2t tT T

1A e e

2 1 1 2A A e(t t ) / T

(55) 238 A92 ZU x Y

234238 Th 23492 91U 90 Y

(56) 206 206238X Y8d 6U

76 8292

206 206pb pb82 or

(57) Energy released per uranium atom = 200 MeV

200 10 200 10 1 6 10 320 106 6 19 13ev .

For -13320x10 2 1 atom

11

-133.232 J λ =10 atoms

320x10

(58)(59) The energy leVel of hydrogen atom corresponding to 10.2 eV is n = 2, n = 1 correponding engery

for the's leVel for helium atom 2

213-6ZE=

n-

1 12 1E E E

13.6 4 ( 13.6 4)E 13.6 54.4 40.8ev4 1



313

(60) For any state 2

o

1 ZeK.E8 E Cn

and Cangatomsl

21 ZeP.E=-4πεo rn

(Total energy in the stote)

E K.E P.E

1 2 .8

ZeE K Eru

(61) For wave longth of second line of Balmer series

2 22(B)

1 1 1 1 1 3RR R2 4 4 16 16

162(B)3R

For wave length of First line of Luman series

2 22(L)

1 1 1 1 1 3RR R1 2 1 4 4

14(L)

3R

2

1

(B) 16 3R 4(L) 3R 4

21

(B) 486.4(C) 121.6mm.4 4

(62)2nr

z For hydrogen atom Z = 1

2r n

1

2

r 1r 4

2 1r 4r 4 0.53 A 2.12 A



314

(63) According comservation of momentummomentum of photon = momentum of rocil atom.

h m

hm

(64)

t1T 2N 1

No 2

tlog 64 log 22t1.8061 0.30102

2 1.8061t 12hrs0.3010

(65) Number of scaltering - particle at angle is

2

o 2 4

Ze 1N N nsm sin 2

14

24

1NQsin 2

1NQsin 2

4 1 41

44 22

1Qsin sin 452N 449QN sin 60 9sin 162

2 14 4N N 28 12.44 129 9



315

(66) nhm 2r

For first Bohr orbit n = 1

hm r 2 2 2

hf4 mr

2 hmr w 2 15f 10

2 hmr (2 f ) 2

(67) 1

1

0.693 0.693 0.693T 0.034652 T 202

1 11

2o

N 1 tN 2 T

2 212

o

N 1 tN 2 T

t12067 1

100 2

233 t1

2 20100

1t20100 2

67

1t201.5 2

1tlog1.5 log 220

1t0.1761 0.301020

10.1761 20t 11.7 min.

0.3010

similary t2 = 31.7-11.7=20min

2 1t t t 31.7 11.7 20min .

(68)(69)(70)

Volume of atomVolumeof nuclear =

3 10 3151

15 33

2

4 1 (10 ) 104 (10 )l3



316

(71)(72)(73)

12

tTN 1 1 72000 1

No 2 2 24000 81N No8

(74) Use formula 2 2

1 1 1R2 n

Putiting n = 2365R

1 4 5R 52 R 36 9

(75) For any atom any state 22

13.6En Zn

For Second excited state n = 3 for Li, Z = 3

2

2 2

13 6 (3)E 13.6ev(3)

(76)

12

12

tT

40T

N 1No 2

1 116 2

12

40T16 (2)

12

40log16 log 2T

12

401.2041 0.3010T

12

40 0.3010T 9.999 10day1.2041



317

(77) A value & Z value89

36 kr

(78) 2 1 13 o6 0 7 1C1 n N e

(79) 2E ( m)C

2E (2m M)C

2

E 2m MC

2EM 2m C

(80) at t = o N = No

12

t T 1 N 1NoN 2 No 16

12

t T 2 NoN4

N 1100 100No 32

12

t T 3 NoN8

3.125

12

t T 4 N0N16

3%

12

t T 5 N0N32

(81)

(82) Wave number = 22

1 1 1 1 1 5RR R2 3 4 9 36

(83)

(84) Ionigation energy of atom E evn

Z6.132

2

For helum Z = 2 2

2

13.6 (2)(1)

=54.4 eV

(85) eerThe energy of r - ray = Rest mass energy + K. E

= (0.5 + 0.5 ) + 0.78= 1.0 + 0.78= 1.78 eV



318

(86) Mass degect m (2mp 2mn) MHe

0015.4)0073.120087.12(m

4.032 4.0015 m 0.030 amu

E m 931.48 mev

0.0305 931.48 28.4Mev

(87) Ans (A) Thomson model(88) Ans (c) 12.75eV

4 113.6 13.6E E E ( ) 0.85 13.6 12.75ev

4 1

(89) In mean life (T) Rest mass = Noe

11 1T min5

t

1 t5

N Noe

No Noe2

1rn2 t5

1 1e t2 5

t 5ln 2

1 12 e t5

2t 5log e

1 12 e t5

(90) 1

2

v 8 :1V

Accotding to conservatron of momentum

1

2

v 8V 1

1 1 2 2m m

1 2

2 1

mm

3

2 2

1 1

V r81 V r

2 1

1 2

r r2 11 r r 2



319

(91) energy reguired to remove aneutron )97.7(16)75.7(17

52.12775.131

ev23.4

(92)(93)(95)

2

1knn

un 2

1n

1

2

k 4k 1

1

2

u 4u 1

k1 = 4k2 u1 = 4u2

K. E. four told P.E also four told. Ans (c)

(96) rA A A 4 A 4z 1z z 1 z 1X Y B B

Ans (A) β,α,γ

(97) 22 2

2 1

1 1 1RZ for anyatomn n

22 2

2 21

1 1 1 1 1 3RZR(1) R2(L) 1 2 4 16 4

11

1 3R 4(L)(L) 4 3R

22 2

2 22

1 1 1 1 1 3RZRZ R2(B) 2 4 4 16 16

2 2

16(B)3RZ

1

2

(L)(B)

2221 z 4 Z 2

4

(98) 2m 1 m 4 m 4n n 2X X n Y



320

(99) dN dN I dNdf

1 21 2I N I N

1

1

IN

1

2

IN

10 1551 2 1

2 21 2 1 20

I f I 3 10 2 10I N 3 10N N N 2 10

(100) 2 2

1 1 1R1 n

2n11R1

21 RR n

2

R R 11Rn

2

R R 1n

1RRn2

1RRn

(101) 1 13 3

o 0R R (a) 2R R (A)

131 9 1 9 A 72

2 A 8 A

(102) Size of nucleus 10-15m

No. of proton in a nucleus Z

Size of atom 10-10m No.of neutrin in nucleus (A-Z)

Ans (B) rd,sc,Pb,qa



NEET UG Physics Atom and Nucleus MCQs - Studiestoday

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