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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54 questions · page 2 of 3
- A. 8,900 years
- B. 6,476 years
- C. 7,000 years
- D. 2,520 years
Explanation: The half-life of a radioactive element is given by the following formula: T1/2 = ln(2) / λ where T1/2 is the half-life, ln(2) is the…
Correct answer: 6,476 years- A. Amount of element present
- B. Temperature
- C. Pressure
- D. None
Explanation: The half-life of a radioactive element depends only on the nature of the radioactive element.
Correct answer: None- A. 12.5%
- B. 8.5%
- C. 87.5%
- D. 25.1%
Explanation: The half-life of a radioactive substance is the time it takes for half of the radioactive atoms in a sample to decay.
Correct answer: 87.5%- A. 1/2
- B. 1/4
- C. 1/8
- D. 1/16
Explanation: The half-life of radium is 1600 years. This means that after 1600 years, half of the radium atoms in a sample will have decayed.
Correct answer: 1/16- A. 10 days
- B. 8 days
- C. 5 days
- D. 6 days
Explanation: Initial mass = 40g Final mass = 1.25g Number of haalf lives = n Initial mass x (1 / 2)n = final mass (1 / 2)n = final mass / initial mass…
Correct answer: 10 days26. A radioactive substance has a half-life of four months, three-fourth of the substance will decay in:
- A. 3 months
- B. 4 months
- C. 8 months
- D. 12 months
Explanation: t1/2 = 4 months Amount of substance left: 1 - 3 / 4 = 0.25 Number of half lives=n (1 / 2)n = amount of substance left (1 / 2)n = 0.25 ==>…
Correct answer: 8 months- A. 3.9 x 10^3 s
- B. 2.9 x 10^-1 s
- C. 2.9 x 10^3 s
- D. 1.6 x 10^-4 s
Explanation: decay constant = 4.3 x 103 s-1 t1/2 = ? t1/2 = 0.693 / decay constant t1/2 = 0.693 / 4.3 x 103 t1/2 = 1.6 x 10-4 s .
Correct answer: 1.6 x 10^-4 s- A. 2 seconds
- B. 5 seconds
- C. 4 seconds
- D. 6 seconds
Explanation: Radioactivity drops to = 1 / 64 of original value Number of half lives = n (1 / 2)n = 1 / 64 (1 / 2)6 = 1 / 64 n = 6 Total time = 30…
Correct answer: 5 seconds- A. 50 mg
- B. 50/√2 mg
- C. 25 mg
- D. Zero
Explanation: Half life = 270 days Total time given = 540 days Number of half-lives => n = 540 / 270 = 2 Initial mass = 100mg Final mass = 100 x (1 /…
Correct answer: 25 mg- A. 100 years
- B. 11460 years
- C. 1000 years
- D. 1200 years
Explanation: The explanation is given below: The C-14 to C-12 ratio in the fossil is one-fourth of the ratio in a living animal's bone, meaning only…
Correct answer: 11460 years- A. 1.58 mg
- B. 1.25 mg
- C. 1.17 mg
- D. 2.56 mg
Explanation: The explanation is given below: Technetium-99m (Tc-99m) has a half-life of 6 hours. You start with 300 mg of it.
Correct answer: 1.17 mg- A. 1: 16
- B. 16: 1
- C. 1: 8
- D. 8: 1
Explanation: To solve this problem, we need to determine the number of half-lives that have passed for each element within the given time frame.
Correct answer: 1: 16- A. 12.5 g
- B. 25 g
- C. 50 g
- D. 100 g
Explanation: To calculate the amount of uranium left after three half-lives, you can use the formula:Final amount=Initial amount×(1/2 )number of…
Correct answer: 50 g- A. 30 days
- B. 20 days
- C. 15 days
- D. 12 days
Explanation: As: N=N0 ×(1/2)t/TGiven that N/N0 =1/32 and t=60 days, we can substitute these values into the equation: 1/32=(1/2)60/TTaking the natural…
Correct answer: 12 days- A. After 1/2 minutes, 1/4 of the isotope remain
- B. After 1 minute, 1/4 of the isotope remain
- C. After 4 minute, 1/4 of the isotope remain
- D. After 4 minute, none of the isotope remain
Explanation: As the Half life is 2 min and the original qunatity of isotopes is 1/2 when we double the time then multiply the half of the new time time…
Correct answer: After 4 minute, 1/4 of the isotope remain- A. After 1/2 minutes, 1/4 of the isotope remain
- B. After 1 minute, 1/4 of the isotope remains
- C. After 4 minutes, 1/4 of the isotope remains
- D. After 4 minute, none of the isotope remain
Explanation: As the half-life is 2 min and the original quantity of isotopes is 1/2, when we double the time,e then multiply the half-life of the new…
Correct answer: After 4 minutes, 1/4 of the isotope remains- A. λ = T1/2
- B. T1/2 = 0.693/λ
- C. λ = T1/2/0.693
- D. λ = T1/2 x 0.693
Explanation: The relationship between the decay constant (λ) and the half-life (T₁/₂) is given by the following equation:T₁/₂ = ln(2) / λ Where:T₁/₂ is…
Correct answer: T1/2 = 0.693/λ- A. 1240 years
- B. 1620 years
- C. 2000 years
- D. 63 years
Explanation: T1/2 = 0.693/ λ = 0.693/(4.28 x 10-4)T 1/2 = 1620 years
Correct answer: 1620 years- A. 1/32No
- B. No/31-No/32
- C. 31/32No
- D. No/32-No/31
Explanation: Np/No = (2n - 1)/ 2n= (25 - 1)/25 = 31/32
Correct answer: 31/32No- A. 0.001 s-1
- B. 0.01 s-1
- C. 0.1 s-1
- D. 1 s-1
Explanation: According to the formula λ=ln(2)/T1/2 =0.693/0.693 =1s-1This is Official Federal MDCAT 2024 question, the question statement and it's…
Correct answer: 1 s-1