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Free Nuclear Physics MCQs with Answers

1,254 Nuclear Physics MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Atomic nuclei contain protons and neutrons, with nuclear size, mass defect and binding energy describing their stability. The work covers alpha, beta and gamma decay, decay equations, half-life and decay rate, along with radiation safety and medical applications such as imaging, radiotherapy and tracers.

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Composition of Atomic NucleiRadioactive DecayHalf-life and Rate of DecayBiological and Medical Uses of Radiation
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1,254 questions · page 48 of 63

941. The radius for an atom is_times the radius of the nucleus.

  • A. 105
  • B. 1010
  • C. 1015
  • D. 1020

Explanation: Ratom= 10-10m & Rnucleus = 10-15mAccording to these values, option 'A' is correct.

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Correct answer: 105

942. When Boron 510B is bombarded by neutrons, α particles are emitted. The resulting nucleus has the mass number:

  • A. 11
  • B. 6
  • C. 7
  • D. 15

Explanation: α particle = He nucleusIt emits an α particle after gaining a neutron.510B + 1n - 24He = 37XSo,the mass number is equal to 7.

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Correct answer: 7

943. Specify the parent nuclei, daughter nuclei, and emitted particle in the given reaction.

  • A. Thorium, Uranium, Neutron
  • B. Uranium, Thorium, Neutron
  • C. Thorium, Uranium, Alpha
  • D. Uranium, Thorium, Alpha

Explanation: The parent nucleus is "23892U" Uranium (146+92=238), Thorium "23490Th"(144+90=234) is the daughter nucleus, and the emitted particle is…

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Correct answer: Uranium, Thorium, Alpha

944. The decay of a nucleus is accompained by the emission of two β-particles and α-radiation. What effect (if any) does this decay have on the proton number and the nucleon number of the nucleus?

  • A. Option A
  • B. Option B
  • C. Option C
  • D. Option D

Explanation: Emission of two beta particles increases the proton number by 2 i.e. after each beta decay, proton number increases by 1.

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Correct answer: Option C

945. An α-particle is bombarded on 14N, as a result 17O is formed. The particle emitted is:

  • A. Neutron
  • B. Electron
  • C. Proton
  • D. Positron

Explanation: The equation below shows the removal of proton.147N + 42He →178O + 11pThus, a proton is emitted.

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Correct answer: Proton

946. Radon-220 is radioactive and decays to Polonium-216 with the emission of an α-particle. The equation for the radioactive decay is shown as 86220Rn→84216Po + 24He. How many neutrons are in the Radon and Polonium nuclei?

  • A. Option A
  • B. Option B
  • C. Option C
  • D. Option D

Explanation: Number of neutrons in Radon =220-86=134Number of neutrons in Polonium=216-84=132

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Correct answer: Option B

947. In alpha emission, the ratio of decrease in proton number to the decrease in neutron number is:

  • A. 2:1
  • B. 1:1
  • C. 1:2
  • D. 4:1

Explanation: In alpha decay, a nucleus emits an alpha particle, which consists of two protons and two neutrons.

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Correct answer: 1:1

948. Radon 86222Rn decays by α-and β-emission to Bismuth 83Bi214.For decay of each nucleus of Radon, how many α-and β-particles are emitted?

  • A. Option A
  • B. Option B
  • C. Option C
  • D. Option D

Explanation: The Radon-222 decays by emitting 2 alpha particles and 1 beta particle.

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Correct answer: Option B

949. The radioactive nucleus undergoes a series of decay according to the scheme (given below). If the mass number and atomic number of A are 180 and 72 respectively, then what are these numbers for A4 ?

  • A. 172 and 69
  • B. 172 and 70
  • C. 174 and 70
  • D. 176 and 70

Explanation: In alpha decay, the atomic number decreases by 2 and the mass number decreases by 4 due to the emission of an alpha particle.

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Correct answer: 172 and 69

950. Neutron decay in the free space is given in the equation below:10n → 11H + 0-1e + [ ]The parentheses represent an:

  • A. Photon
  • B. Neutrino
  • C. Graviton
  • D. Antineutrino

Explanation: Neutron decay is a type of radioactive decay that occurs when a neutron inside the nucleus of an atom spontaneously decays into a proton…

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Correct answer: Antineutrino

951. The masses of two radioactive substances are the same and their half-lives are 1 year and 2 years respectively. The ratio of their activities after six years will be:

  • A. 1:4
  • B. 4:1
  • C. 1:8
  • D. 8:1

Explanation: To find the ratio of their activities after six years, we can use the formula for radioactive decay:Activity = Initial activity *…

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Correct answer: 8:1

952. Let T be the mean life of a radioactive sample. 75% of the active nuclei present in the sample initially will decay in time:

  • A. 2T
  • B. 4T
  • C. 1/2(ln 2)T
  • D. 2(ln 2)T

Explanation: When 75% decays, 25%is left un-decayed. This requires a time t=2T1/2 , where T1/2 = half-life = ln2/λ.Also, T1/2 = 1/λ.So, t = 2(ln2/λ) =…

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Correct answer: 2(ln 2)T

953. In a sample of radioactive material, what fraction of the initial number of active nuclei will remain undisintegrated after the half-life of the sample?

  • A. 1/4
  • B. 1/ √2
  • C. 1/2 √2
  • D. √2 - 1

Explanation: According to the formula and the given data, the fractional un-decay would be 1/ √2.

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Correct answer: 1/ √2

954. Relation for half-life of any radioactive element is:

  • A. T1/2 = λln2
  • B. λ = T1/2 ln2
  • C. T1/2 = ln2/λ
  • D. T1/2= λ/ln2

Explanation: As we know that: λT1/2 = ln2 T1/2 = ln2/λ

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Correct answer: T1/2 = ln2/λ

955. The half-life period of Radium is 1600 years. Its average lifetime will be:

  • A. 3200 years
  • B. 2319 years
  • C. 4800 years
  • D. 4217 years

Explanation: Average life : 1/ λ = T1/2 / 0.693 = 1600/ 0.693 = 2308 yearsThis is approximately equal to 2319 years.

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Correct answer: 2319 years

956. The decay constant of a radioactive element is 0.01 per second. Its half-life period is:

  • A. 0.693 sec
  • B. 6.93 sec
  • C. 69.3 sec
  • D. 692 sec

Explanation: T1/2 = 0.693/λ = 0.693/0.01 = 69.3 seconds

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Correct answer: 69.3 sec

957. What is the ratio of un-decayed and decayed nuclei of a radioactive element after 3 half-lives have elapsed?

  • A. 1/7
  • B. 7/8
  • C. 7
  • D. 8/7

Explanation: NR = No(1/2n) and ND = No (2n -1)/2nNR/ND = (1/8) x (8/7)= 1/7Thus, option 'A' is correct.

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Correct answer: 1/7

958. Which of the following is the percentage of the orignal quantity of a radioactive material left five half-lives approximately?

  • A. 3%
  • B. 5%
  • C. 10%
  • D. 20%

Explanation: After 5 half-lives remaining amount=1/25 = 1/32Percentage of remaining amount= (1/32)×100 = 3%

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Correct answer: 3%

959. Which one of the following can be preferred for the treatment of skin?

  • A. β-particles
  • B. X-rays
  • C. ϒ-radiation
  • D. α-rays

Explanation: ϒ-radiation can be preferred for the treatment of skin. Gamma radiation consists of high-energy photons and is highly penetrating.

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Correct answer: ϒ-radiation

960. Radio-isotope Cobalt which emits high-energy γ-rays is used for the treatment of:

  • A. Fever
  • B. Liver
  • C. Bones
  • D. Cancer

Explanation: Cobalt-60 is primarily used in radiation therapy for the treatment of cancer.

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Correct answer: Cancer
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