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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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

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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
(d) Gamma ray spectroscopy

Concept Questions :-

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Difficulty Level:

A radioactive decay chain starts from ${}_{93}{}^{237}\mathrm{Np}$ and produces ${}_{90}{}^{229}\mathrm{Th}$ by successive emissions. The emitted particles can be
(a) Two $\mathrm{\alpha }$-particles and one $\mathrm{\beta }$-particle
(b) Three ${\mathrm{\beta }}^{+}$ particles
(c) One $\mathrm{\alpha }$ particle and two ${\mathrm{\beta }}^{+}$ particles
(d) One $\mathrm{\alpha }$ particle and two ${\mathrm{\beta }}^{-}$ particles

Concept Questions :-

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The half-life of a sample of a radioactive substance is 1 hour. If $8×{10}^{10}$ atoms are present at t = 0, then the number of atoms decayed in the duration t = 2 hour to t = 4 hour will be
(a) $2×{10}^{10}$          (b) $1.5×{10}^{10}$
(c) Zero               (d) Infinity

Concept Questions :-

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Difficulty Level:

Carbon dating is best suited for determining the age of fossils if their age in years is of the order of
(a) ${10}^{3}$             (b) ${10}^{4}$
(c) ${10}^{5}$             (d) ${10}^{6}$

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A count rate meter shows a count of 240 per minute from a given radioactive source. One hour later the meter shows a count rate of 30 per minute. The half-life of the source is

(a) 120 min                   (b) 80 min
(c) 30 min                     (d) 20 min

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Difficulty Level:

The half-life of a radioactive substance is 40 years. How long will it take to reduce to one fourth of its original amount and what is the value of decay constant
(a) 40 year, 0.9173/year            (b) 90 year, 9.017/year
(c) 80 year, 0.0173 year            (d) None of these

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Difficulty Level:

A radioactive material has a half life of 10 days. What fraction of the material would remain after 30 days

(a) 0.5               (b) 0.25
(c) 0.125            (d) 0.33