1 Curie (Ci) = ---------

1. 3.7 x 10¹⁰ dps
2. 3.7 x 10¹⁰ Bq
3. 37 GBq
4. all of these
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Answer: D
Explanation:
• All of these are equivalent.
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1 Becquerel (Bq) = --------- Curie (Ci).

1. 2.7 x 10^-11
2. 3.7 x 10^-11
3. 2.7 x 10¹¹
4. 7.03 x 10^-11
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Answer: A
Explanation:
• N/A
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Curie is a measur of the:

1. total energy absorbed by an object exposed to a radioactive source
2. number of disintegrations per second of a radioactive substance
3. number of alpha particles emitted by exactly one gram of a radioactive substance
4. lethal threshold for radiation exposure
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Answer: B
Explanation:
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The time required for the radioactivity of an isotope to be reduced to half of its original amount is called:

1. radioactive dating
2. average life
3. half-life
4. none of these
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Answer: C
Explanation:
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The radioactive decay of an isotope is a ------ reaction:

1. first order
2. second order
3. third order
4. may be of any order
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Answer: A
Explanation:
• Because it involves only a single decaying nucleus.
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The half-life period of a radioactive isotope is:

1. directly proportional to its initial concentration
2. inversely proportional to its initial concentration
3. independent of its initial concentration
4. directly proportional to the square of its initial concentration
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Answer: C
Explanation:
• Radioactive decay is a first order reaction and half life `(t_1/2)_n prop 1/(a^(n-1))` where "n" is order of reaction and "a" is initial concentration of radioactive substance.
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The half-life period of a radium is 1620 years. In what time its 1 g will reduce to 0.25 g:

1. 1620 years
2. 3240 years
3. 4860 years
4. 2430 years
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Answer: B
Explanation:
• Atfter first half-life (1620 years), its 1 g will reduce to 0.5 g and after second half-life (1620 x 2 = 3240 years) it will reduce to 0.25 g.
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The unit of half-life period is:

1. mg sec^-1
2. g min^-1
3. time^-1
4. g sec^-1
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Answer: C
Explanation:
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The half-life of sulphur-35 is 88 days. If 8.0 gram of it exists on first day, what amount will remain after 264 days?

1. 2.0 g
2. 1.0 g
3. 0.5 g
4. 4.0 g
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Answer: B
Explanation:
• After 3 half-lives (88 x 3 = 264 days), the amount left will be = `(8g)/2^3=8/8` = 1 g, Genera Formula = `(Amount)/2^n` Where n is number of half-lives.
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The number of disintegrations or the rate of decay per unit time is called:

1. rate of radioactive decay
2. radioactive dating
3. average half-life
4. activity of a radioactive substance
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Answer: D
Explanation:
• N/A
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