The half-life of uranium-235 is about:

1. 700 million years
2. 7 million years
3. 4.5 billion years
4. 2.45 million years
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Answer: A
Explanation:
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The half-life of uranium-238 is about:

1. 700 million years
2. 7 million years
3. 4.5 billion years
4. 2.45 million years
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Answer: C
Explanation:
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The half-life of uranium-234 is about:

1. 700 million years
2. 7 million years
3. 4.5 billion years
4. 245500 years
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Answer: D
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The radioactive equilibrium differs from a chemical equilibrium in that it is:

1. irreversible
2. reversible
3. may be recersible or irreversible
4. established in a very long time
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Answer: A
Explanation:
• Radioactive equilibrium is always irreversible.
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The age of an old piece of a wood can be determined by:

1. average life
2. Decay constant
3. radioactive dating
4. can not be determined
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Answer: C
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The atmosphere contains which oxide of carbon?

1. ¹⁴CO₂
2. ¹²CO₂
3. both a & b
4. none of these
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Answer: C
Explanation:
• Atmosphere contains radioactive ¹⁴CO₂ and ordinary ¹²CO₂ in a fixed ratio.
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Alive plant takes up which oxide of carbon?

1. ¹⁴CO₂
2. ¹²CO₂ only
3. both a & b
4. CO
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Answer: C
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Radioactive dating technique involves the use of which isotope of carbon?

1. C-14
2. C-13
3. C-12
4. all of these
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Answer: A
Explanation:
• In old objects, Carbon-12 remains unchanged while carbon-14 decays by beta-emission.
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The age of an old piece of a wood can be calculated by knowing the concentration of:

1. C-14 in a given sample of old wood
2. C-14 in a living plant
3. C-14/C-12 ratio
4. all of these
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Answer: D
Explanation:
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The new method for determining the age of old wood by spectrometric method involves the measurement of:

1. radioactivity
2. C-14/C-12 ratio
3. average life
4. half-life
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Answer: B
Explanation:
• Age is determined by the formula `t = log ((14_(C_0))/14_(C_t)) x 2.303/lamda`. Where `14_(C_0)` is concentration of C-14 in fresh plant at time t = 0 and `14_(C_t)` is concentration of C-14 in the old piece of wood at time "t".
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