Atomic Nucleus|. Practice MCQs Physics for Mdcat By Engr. Kamran Soomro | mosaicbro.com

Atomic Nucleus|. Practice MCQs Physics for Mdcat By Engr. Kamran Soomro

7 of 114 questions (Page 16 of 17)

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106 The rate of decay of a radioactive substance:
Correct Answer: A
Explanation: Decay rate follows $\frac{dN}{dt} = -\lambda N$, an exponential decrease.
107 Different radioactive materials have:
Correct Answer: B
Explanation: Half-lives vary widely among isotopes (e.g., seconds to billions of years).
108 The half life of a radioactive element is 6 min. If the initial count rate is 824 per min, how long will it take to reach count rate 206:
Correct Answer: A
Explanation: 206 cpm = 1/4 of initial rate = 2 half-lives = 12 min.
109 The time required for a radioactive material to decrease in activity by one half is called:
Correct Answer: B
Explanation: Half-life ($t_{1/2}$) is the time for activity to halve.
110 After alpha decay the mass of the nucleus:
Correct Answer: B
Explanation: Alpha decay reduces mass number by 4 (loss of $^4_2\text{He}$).
111 Neutrons are:
Correct Answer: D
Explanation: Neutrons have no electric charge.
112 Alpha particles are:
Correct Answer: B
Explanation: Alpha particles are $^4_2\text{He}$ nuclei.
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