The activity of a sample of a radioactive material is ${\mathrm{A}}_{1}$, at time ${\mathrm{t}}_{1}$ and ${\mathrm{A}}_{2}$ at time ${\mathrm{t}}_{2}$ (${\mathrm{t}}_{2}$>${\mathrm{t}}_{1}$). If its mean life T, then
(a) ${\mathrm{A}}_{1}{\mathrm{t}}_{1}={\mathrm{A}}_{2}{\mathrm{t}}_{2}$            (b) ${\mathrm{A}}_{1}-{\mathrm{A}}_{2}={\mathrm{t}}_{2}-{\mathrm{t}}_{1}$
(c) ${\mathrm{A}}_{2}={\mathrm{A}}_{1}{\mathrm{e}}^{\left({\mathrm{t}}_{1}-{\mathrm{t}}_{2}\right)/\mathrm{T}}$    (d) ${\mathrm{A}}_{2}={\mathrm{A}}_{1}{\mathrm{e}}^{\left({\mathrm{t}}_{1}/{\mathrm{t}}_{2}\right)\mathrm{T}}$

Concept Questions :-

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Difficulty Level:

Nucleus produced due to $\mathrm{\alpha }$-decay of the nucleus ${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X}$ is

(a) ${}_{\mathrm{Z}+2}{}^{\mathrm{A}+4}\mathrm{Y}$                     (b) ${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{Y}$
(c) ${}_{\mathrm{Z}-2}{}^{\mathrm{A}-4}\mathrm{Y}$                     (d) ${}_{\mathrm{Z}-4}{}^{\mathrm{A}-2}\mathrm{Y}$

Concept Questions :-

Types of decay
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Difficulty Level:

Which of the following processes represents a gamma-decay

(a) ${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X}+\mathrm{\gamma }\to {}_{\mathrm{Z}-1}{}^{\mathrm{A}}\mathrm{X}+\mathrm{a}+\mathrm{b}$
(b) ${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X}+{}_{0}{}^{1}\mathrm{n}\to {}_{\mathrm{Z}-2}{}^{\mathrm{A}-3}\mathrm{X}+\mathrm{c}$
(c) ${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X}\to {}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X}+\mathrm{f}$
(d)

Concept Questions :-

Types of decay
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Difficulty Level:

The half-life of ${}_{215}\mathrm{At}$ is 100 $\mathrm{\mu s}$. The time taken for the radioactivity of a sample of ${}_{215}\mathrm{At}$ to decay to 1/16th of its initial value is
(a) 400 $\mathrm{\mu s}$               (b) 6.3 $\mathrm{\mu s}$
(c) 40 $\mathrm{\mu s}$                 (d) 300 $\mathrm{\mu s}$

Concept Questions :-

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Difficulty Level:

The half-life of a radioactive substance is 48 hours. How much time will it take to disintegrate to its $\frac{1}{16}$th part

(a) 12 h             (b) 16 h
(c) 48 h             (d) 192 h

Concept Questions :-

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Difficulty Level:

A radioactive substance has an average life of 5 hours. In a time of 5 hours
(a) Half of the active nuclei decay
(b) Less than half of the active nuclei decay
(c) More than half of the active nuclei decay
(d) All active nuclei decay

Concept Questions :-

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Difficulty Level:

Which of the following radiations has the least wavelength

(a) X-rays              (b) $\mathrm{\gamma }$-rays
(c) $\mathrm{\beta }$-rays              (d) $\mathrm{\alpha }$-rays

Concept Questions :-

Types of decay
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Difficulty Level:

A radioactive sample at any instant has its disintegration rate 5000 disintegration per minute. After 5 minutes, the rate is 1250 disintegrations per minute. Then, the decay constant (per minute) is
(a) 0.8 In 2                (b) 0.4 In 2
(c) 0.2 In 2                (d) 0.1 In 2

Concept Questions :-

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Difficulty Level:

A nucleus with Z = 92 emits the following in a sequence:
$\mathrm{\alpha },{\mathrm{\beta }}^{-},{\mathrm{\beta }}^{-},\mathrm{\alpha },\mathrm{\alpha },\mathrm{\alpha },\mathrm{\alpha },\mathrm{\alpha },{\mathrm{\beta }}^{-},{\mathrm{\beta }}^{-},\mathrm{\alpha },{\mathrm{\beta }}^{+},{\mathrm{\beta }}^{+},\mathrm{\alpha }$. The Z of the resulting nucleus is
(a) 74              (b) 76
(c) 78              (d) 82

Concept Questions :-

Types of decay
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Difficulty Level:

Radioactive nuclei that are injected into a patient collect at certain sites within its body, undergoing radioactive decay and emitting electromagnetic radiation. These radiations can then be recorded by a detector. This procedure provides an important diagnostic tool called
(a) Gamma camera
(b) CAT scan