Free Half-life and Rate of Decay MCQs with Answers
54 Half-life and Rate of Decay MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Half-life is the time required for half the unstable nuclei in a sample to decay, and it remains constant for a particular radioactive nuclide. Questions use the exponential decay law, decay constant, activity, remaining quantity and mean life. Radioactive decay is random for individual nuclei but predictable for large samples.
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- A. the whole sample decays
- B. half the undecayed nuclei present decay
- C. the activity becomes zero
- D. the mass of the sample halves
Explanation: Decay is a random process with a constant probability per nucleus per unit time, so a fixed fraction rather than a fixed number decays in…
Correct answer: half the undecayed nuclei present decay2. A radioactive sample has a half life of 8 days. The fraction remaining undecayed after 24 days is
- A. one half
- B. one quarter
- C. one eighth
- D. one sixteenth
Explanation: Twenty four days is three half lives, so the sample is halved three times, leaving one half multiplied by one half multiplied by one half…
Correct answer: one eighth- A. becquerel
- B. gray
- C. sievert
- D. coulomb
Explanation: One becquerel is one disintegration per second, so it measures how fast the source is decaying.
Correct answer: becquerel- A. carbon 14 is stable
- B. living things take in carbon 14 while alive, and it then decays with a known half life after death
- C. all carbon is radioactive
- D. carbon 14 is produced in the body
Explanation: While an organism lives it exchanges carbon with its surroundings and holds the atmospheric ratio of carbon 14 to carbon 12, but after…
Correct answer: living things take in carbon 14 while alive, and it then decays with a known half life after death- A. 1/2
- B. 1/4
- C. 1/8
- D. 1/16
Explanation: Each half life halves the number of undecayed nuclei, so three of them give a half multiplied by a half multiplied by a half, which is one…
Correct answer: 1/8- A. 1/2 life of radioactive element
- B. 2/3 life of radioactive element
- C. 1/4 life of radioactive element
- D. 2/5 life of radioactive element
Explanation: The half life is the interval in which half the undecayed nuclei present decay, and because decay is random with a constant probability…
Correct answer: 1/2 life of radioactive element- A. Hardness
- B. Density
- C. Mass
- D. Half life
Explanation: Each radioactive isotope has a characteristic half-life, the time required for half of a sample's unstable nuclei to decay, so measuring…
Correct answer: Half life- A. 0.0625 of the original amount
- B. 0.5 of the original amount
- C. 0.25 of the original amount
- D. 0.125 of the original amount
Explanation: 2 half-lives have passed so one-fourth of the sample remains.
Correct answer: 0.25 of the original amount- A. 1
- B. 1/2
- C. 3/4
- D. 1/4
Explanation: Correct option is C. The correct solution is given as:
Correct answer: 3/4- A. Diffuse
- B. Decompose
- C. Disturbed
- D. Decay
Explanation: The term "decay" is the correct option. The half-life of a radioactive element is the time it takes for half of the radioactive atoms in a…
Correct answer: Decay- A. 2400 years
- B. 3200 years
- C. 6400 years
- D. 4800 years
Explanation: Two half lives later, 100g of gamma rays will be reduced to 25g. 100/2² = 25 The half life of Radium = 1600 yearsTime taken = 2×1600 =…
Correct answer: 3200 years- A. 67 %
- B. 87.5%
- C. 82.5%
- D. 77%
Explanation: To solve this problem, we first determine how many half-lives have passed in 15 days.
Correct answer: 87.5%- A. 120 minutes
- B. 90 minutes
- C. 30 minutes
- D. 60 minutes
Explanation: N(t) = N0 * (1/2)^(t / T),In this case, N(t) is 125 per minute, No is 1000 per minute, and T is 40 minutes.
Correct answer: 120 minutes- A. 23 years
- B. 1000 years
- C. 1200 years
- D. 5730 years
Explanation: The explanation is given below: The half-life of Carbon-14 (^(14)C) is approximately 5,730 years.
Correct answer: 5730 years- A. 10 days
- B. 15 days
- C. 3 days
- D. 5 days
Explanation: The half-life of a radioactive substance can be determined based on the time it takes for the activity (or the number of radioactive…
Correct answer: 5 days- A. 1/32
- B. 1/16
- C. 1/8
- D. 1/4
Explanation: The explanation is given below: To find the fraction of the original radioactive isotope of nitrogen (N) remaining after 32.5 seconds, we…
Correct answer: 1/32- A. 9 years
- B. 8 years
- C. 6 years
- D. 24 years
Explanation: The number of atoms of a radioactive substance decreases by half after each half-life.
Correct answer: 9 years- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: The half-life of a radioactive substance is the time it takes for the number of radioactive atoms to decrease to half of its original…
Correct answer: Option B- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: The half-life of a radioactive material is the time it takes for half of the radioactive atoms in a sample to decay.
Correct answer: Option B- A. 500, 125
- B. 125,500
- C. 103, 103
- D. 100, 10
Explanation: The decay rate at t=0 is 1000Hz. at t=1=1000/21 =500/sec. at t=3=1000/23 =125/sec.
Correct answer: 500, 125Half-life and Rate of Decay MCQs: common questions
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