# MCQ Questions Chapter 13 Nuclei Class 12 Physics

Please refer to MCQ Questions Chapter 13 Nuclei Class 12 Physics with answers provided below. These multiple-choice questions have been developed based on the latest NCERT book for class 12 Physics issued for the current academic year. We have provided MCQ Questions for Class 12 Physics for all chapters on our website. Students should learn the objective based questions for Chapter 13 Nuclei in Class 12 Physics provided below to get more marks in exams.

## Chapter 13 Nuclei MCQ Questions

Please refer to the following Chapter 13 Nuclei MCQ Questions Class 12 Physics with solutions for all important topics in the chapter.

MCQ Questions Answers for Chapter 13 Nuclei Class 12 Physics

Question. If radium has half-life of 5 years. Thus for a nucleus in a sample of radium, the probability of decay in ten years is:
(a) 50%
(b) 75%
(c) 100%
(d) 60%

B

Question. The half-life of radioactive substance is 3.8 days. The time at the end of which (1/20)th of the radioactive substance will remain undecayed is: (given log10 e = 0.4343)
(a) 13.8 days
(b) 16.5 days
(c) 33 days
(d) 76 days

B

Question. n alpha particles per second are emitted from N atoms of a radioactive element. The half-life of radioactive element is :

C

Question. The half-life period of radium is 1600 years. Its average life time will be :
(a) 3200 year
(b) 4800 year
(c) 2319 year
(d) 4217 year

C

Question. At certain time the activity of three radioactive materials are in the ratio of 3 : 4 : 5. What will be the ratio of their activities at any further date?
(a) 1 : 2 : 3
(b) 2 : 3 : 4
(c) 3:4:5
(d) 5 : 6 : 8

C

Question. The nucleus of nucleon number 16, has nuclear radius 3 x 10~15 m, then the radius of nucleus having nucleon number 128 is :
(a) 3 x 10-15 m
(b) 1.5 x 10~15 m
(c) 6 x 10~15 m
(d) 4.5 x 10~15 m

C

Question. A particle moving with a velocity (1/10)th of light will cross a nucleus in about:
(a) 10-8 sec
(c) 10~47 sec
(b) 10~12 sec
(d) 10-21 sec

D

Question. 20% of a radioactive substance decay in 10 days. The amount of the original material left after 30 days is :
(a) 51.2%
(b) 62.6%
(c) 15%
(d) 21.27%

A

Question. A parent nucleus imp decays into a daughter nucleus D through a emission in the following way imp → D + a. The subscript and superscript on the daughter nucleus D will be written as :

D

Question. The number of nuclei present in a mass m gram of radioactive element of mass number A is :
(a) 6.02x 1023 m/A
(b) 6.6×1034 m/A
(c) 6.02×1023 mA
(d) 6.02xl034 A/m

A

Question. The activity of a sample of radioactive material is A1 at time t1 and A2 at time t2 (t2 > t1). Its mean life is T such that:

C

Question. In the nucleus of 11Na23, the number of protons, neutrons and electrons is:
(a) 11, 12, 11
(b) 23, 12, 11
(c) 12, 11, 0
(d) 23, 11, 12

A

Question. A sample contains one kg O19 nuclei. The sample decays according to following equation. O19 → F19 + e + v The mass of sample after one half-life period is :
(a) lesser than 1/2 kg
(b) equal to 1/2 kg
(c) slightly less than 1 kg
(d) equal to 1 kg

C

Question. The number of C14 atoms in a sample is 100. The half-life period of C14 is 5730 year. The number of C14 atoms in the sample after 5730 year :
(a) must be equal to 50
(b) must be equal to 100
(c) may be equal to 90
(d) must be equal to 90

C

Question. The alpha and beta particles cause ionisation because of :
(a) photoelectric emission
(b) compton collision
(c) pair production
(d) the electrostatic force ,

D

Question. In nuclear reaction

where M denotes :
(a) electron
(b) positron
(c) proton
(d) neutron

D

Question. In the given reaction

(a) a,β,Y
(b) β,a,y
(c) Y,a,β
(d) β, y, a

B

Question. The critical mass of fissionable uranium 235 can be reduced by:
(a) surrounding it by neutron absorbing material
(b) surrounding it by neutron reflecting material
(c) heating the material

B

Question. In how many months, (3/4)th of the substance will decay, if half-life of the radioactive substance is 2 months?
(a) 4 month
(b) 6 month
(c) 8 month
(d) 14 month

A

Question. The radioactive decay rate of a radioactive element is found to be 103 disintegrations per second at a certain time. If the half life of the element is one second, the decay rate after three second is :
(a) 1000
(b) 250
(c) 1000/3
(d) 125

D

Question. The count rate of a radioactive nuclei falls from 992 counts per minute to 62 counts per minute in 10 hour. The half-life of the element is :
(a) 1 hour
(b) 2.5 hour
(c) 5 hour
(d) 6 hour

B

Question. The half-life of a freshly prepared radioactive sample is 2 hours. If the sample emits radiation of intensity which is 32 times the permissible safe level, then the minimum time taken after which it would be possible to work safely with source is :
(a) 8 hour
(b) 10 hour
(c) 16 hour
(d) 2 hour

B

Question. When number of nucleons in nuclei increases, the binding energy per nucleon :
(a) increases continuously with mass number
(b) decreases continuously with mass number
(c) remains constant with mass number
(d) first increases and then decreases with increase of mass number

D

Question. The radius of Na23 nucleus is :
(a) 3.125 xl0~15m
(b) 23xl0-15m
(c) 11 x 1015 m
(d) 1.1 x l013 m

A

Question. The mass of electron in atomic mass unit is :
(a) 0.0005498
(b) 0.5119
(c) 0.5498
(d) none of these

A

Question. The atomic mass of AI27 is 26.9815 amu. The mass of electron is 0.0005498 amu. The rest mass energy of AI27 nucleus is
(a) 1862 MeV
(b) 25119.78 MeV
(c) 25113.12 MeV
(b) none of these

C

Question. The atomic mass of B10 is 10.811 amu. The binding energy of B10 nucleus is [Given : The mass of electron is 0.0005498 amu, the mass of proton is mp = 1.007276 amu and the mass of neutron is mn = 1.008665 amu] :
(a) – 678.272 MeV
(b) 678.932 MeV
(c) 378.932 MeV
(d) none of these

A

Question. The binding energy of Na23 is [Given : Atomic mass of Na23 is 22.9898 amu and that of 1H1 is 1.00783 amu. The mass of neutron = 1.00867 amu] :
(a) 931 MeV
(b) 186.54 MeV
(c) 5.38 MeV
(d) none of these

B

Question. The binding energies per nucleon are 5.3 MeV, 6.2 MeV and 7.4 MeV for the nuclei with mass numbers 3, 4 and 5 respectively. If one nucleus of mass number 3 combines with one nucleus of mass number 5 to give two nuclei of mass number 4, then :
(a) 0.3 MeV energy is absorbed
(b) 0.3 MeV energy is released
(c) 28.1 MeV energy is absorbed
(d) 3.3 MeV energy is absorbed

D

Question. The mass number of a nucleus is :
(a) always less than its atomic number
(b) always more than its atomic number
(c) sometimes equal to its atomic number
(d) all of the above

C

Question. When the atomic number A of a nucleus increases :
(a) initially the neutron-proton ratio is constant
(b) initially the neutron-proton ratio increases and then decreases
(c) initially the binding energy per nucleon increases and then decreases
(d) the binding energy per nucleon increases when neutron proton ratio increases

C

Question. The ratio of half-life to the mean life of a radioactive sample, if X be the decay constant of a radioactive sample is :
(a) 0.693
(b) 0.746
(c) 1/0.693
(d) (0.693)2

A

Question. A particular nucleus in a large population of identical radioactive nuclei survives 10 half lives of that isotopes. The probability that this surviving nucleus will survive the next half-life is :
(a) 1/10
(b) 2/5
(c) 1/2
(d) 1/210

C

Question. Which of the following is wrong about β+– emission?
(a) Proton convert into neutron
(b) β+-emission is associated with emission of anti-neutrino
(c) β+-emission is caused by decay or π+
(d) No change in masb number due to this emission

C

Question. p-emission must be associate with :
(a) neutrino emission
(b) anti-neutrino emission
(c) positron emission
(d) proton emission

B

Question. Radioactivity can be effected by :
(a) temperature
(b) pressure
(d) all of these

C

Question. Which of the following is correct statement?
(a) Average life is time in which no disintegration takes place
(b) Average life is the average time upto v.’hich the unstable nuclei exist, before its disintegration
(c) {3/4 is the time in which one-fourth of radionuclide will decay
(d) The product of half-life and average life have same value for all radio isotopes

B

Question. The penetrating powers of a, P and y radiations, in decreasing order are:
(a) y, a, β
(b) y, β, a
(c) a,β,y
(d) β, y, a

B

Question. A sample of radioactive material has mass m, decay constant λ and molecular weight M. Avagadro’s constant = NA. The initial activity of the sample is :
(a) λm
(b) λm//M
(c) λmNA/M
(d) mNAeλ

C

Question. Four vessels A, B, C and D contain respectively 20 g-atom (t 1/2 = 5 hour), 2 g-atom (f1/2 = 1 hour), 5 g-atom (t1/2 = 2hour) and 10 g-atom (f1/2 = 3hour) of different radio nuclides in the beginning, the maximum activity would be exhibited by the vessel is :
(a) A
(b) B
(c) C
(d) D

A

Question. The half-life of Tc99 is 6 hour. The activity of Tc99 in a patient, 60 hour after receiving an injection containing this radioisotope is at least 0.125 pci. What was the minimum activity (in pci) of the sample injected?
(a) 1.25 pci
(b) 12.5 pci
(c) 128 pci
(d) 125 pci

C

Question. A radioactive sample has an initial activity of 50 dpm, 20 minute later, the activity is 25 dpm. How many atoms of the radioactive nuclide were there originally?
(a) 20
(b) 1000
(c) 1443
(d) 2

C

Question. Half-life period of a given radioactive sample is t. Its average life would be :

B

Question. Choose the correct option, if Tn and Tm denote the half-value period and the mean-value period, respectively of a radioactive element:
(a) Tn = Tm
(b) Tn > Tm
(c) Tn < Tm
(d) Tn > Tm

C

Question. A heavy nucleus (mass number = A) splits into two new nuclei, whose mass numbers are in the ratio 3 :2. The ratio of radii of these new nuclei are :
(a) 3:2
(b) 2:3
(c) 31/3:21/3
(d) 21/3:31/3

C

Question. The rest mass energy of electron is :
(a) 0.8 MeV
(b) 1.66 amu
(c) 0.5119 MeV
(d) none of these

C

Question. The half-life of radium is 1600 years. The number of atoms that will decay from 1 g sample of radium per second is (Given : Atomic weight of radium = 226) :
(a) 3.6x10
(c) 4.2x10
(b) 7.2x10
(d) 14.6x10

A

Question. How long will it take for 75% of the atoms of a certain radioactive element, originally present to disintegrate? The half-life of the element is 10 days :
(a) 240 days
(b) 3.6 days
(c) 15.6 days
(d) 4.15 days

D

Question. One milligram of matter converted into energy will give :
(a) 90 J
(b) 9 x 10 J
(c) 9xl010J
(d) 9 x10 J

C

Question. In the fission of uranium, 0.5 g mass disappears. The energy obtained is:
(a) 1.25 kWh
(b) 1.25 x 107kWh
(c) 0.25 kWh
(d) 1.25 x 104 kWh

B

Question. What should be the activity of a radioactive sample of mass m and decay constant λ, after time t ? Take molecular weight of the sample be M and the Avagadro number be NA :

B

Question. The activity of a radioactive sample goes down to about 6% in a time of 2 hours. The half life of the sample in minutes is about :
(a) 30
(b) 15
(c) 60
(d) 120

D

Question. Mark the correct option, for the substance which cannot be emitted by radioactive substances during their decay :
(a) electrons
(b) protons
(c) neutrinoes
(d) helium nuclei

B

Question. The most stable nucleus should have :
(a) even number of protons and odd number of neutrons
(b) odd number of neutrons and odd number of protons
(c) even number of protons and even number of neutrons
(d) even number of neutrons and odd number of protons

C

Question. Nuclear isomers differ in :
(a) number of protons
(b) number of neutrons
(c) number of n
(d) energy

B

Question. a, β and y radiations come out of a radioactive substance :
(a) when it is heated
(b) when put in atomic reactor
(c) spontaneously
(d) under pressure

C

Question. A radio isotope disintegrates both by a and P-emission. The half-life with respect to each decay is T1 and T2, respectively. The overall half-life, T with respect to disintegration will be :

C

Question. The binding energies per nucleon for a deuteron and an ot-particle are x\ and x2 respectively. What will be the energy Q released in the reaction ? 1H2 + 1H2 2He4 + Q
(a) 4(x-1 + x2)
(b) 4(X2 – x:)
(c) 2(X1 + X2)
(d) 2(x2-x1)

B

Question. A sample of a radioactive element of 16 g is taken from Kota to Patna in 2 hour and U was found that 1 g of the element remained undisintegrated. Half-life of the element is :
(a) 2 hr
(b) 1 hr
(c) (1/2) hr
(d) (1/4) hr

C

Question. A radioactive sample decays with an average life of 2 min. An inductor is shorted through a resistance R, then the value of resistance R for which the ratio of the current through the resistance to the activity of the radioactive sample remains constant is :
(a) 10In2 Ω
(b) 5 Ω
(c) 10 Ω
(d) 5 In 2 Ω

B

Question. For measuring the activity of a radioactive sample, a count rate meter is used. At certain observation, count rate meter recorded 5050 counts per minute but after 10 minutes later, the count rate showed 2300 counts per minute. The disintegration constant (λ.) is :
(a) 0.065 per min
(b) 0.078 per min
(c) 0.24 per min
(d) 0.868 per min

B

Assertion-Reason Questions

In the following questions, a statement of Assertion (A) is followed by a statement of Reason (R). Choose the correct answer out of the following choices.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false and R is also false.

1. Assertion (A): Density of all nuclei is same.
Reason (R): The radius of nucleus is directly proportional to the cube root of mass number.

A

2. Assertion (A): Neutrons penetrate matter more readily as compared to proton.
Reason (R): Neutrons are slightly more massive than protons.

B

3. Assertion (A): Energy is released in nuclear fission.
Reason (R): Total binding energy of fission fragments is larger than the total binding energy of the parent nucleus.

A

4. Assertion (A): The binding energy per nucleon, for nuclei with mass number A > 100 decreases with A.
Reason (R): The nuclear forces are weak for heavy nuclei.

C

5. Assertion (A): The elements produced in the fission are radioactive.
Reason (R): The fragments have abnormally high proton to neutron ratio.

C

6. Assertion (A): The fusion process occurs at extremely high temperatures.
Reason (R): For fusion of two nuclei, enormously high kinetic energy is required.

A

7. Assertion (A): A neutrino is chargeless and has a spin.
Reason (R): Neutrino exists inside the nucleus.

C

8. Assertion (A): β-particles emitted in radioactivity are simply very fast-moving electrons.
Reason (R): β-particles are orbital electrons which are emitted by receiving energy from the sun.

C

9. Assertion (A): β-particles have continuous energies starting from zero to a certain maximum value.
Reason (R): The total energy released in decay of a radioactive element is shared by electron and neutrino. The sum of energies of electron and neutrino is constant.