Dual Nature Of Radiation And Matter Ques 47
47. The momentum of a photon of energy $1 $ $MeV$ in $kg m / s$, will be
(a) $7 \times 10^{-24}$
(b) $10^{-22}$
(c) $5 \times 10^{-22}$
(d) $0.33 \times 10^{6}$
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Answer:
Correct Answer: 47.(c)
Solution:
- (c) $1$ $ MeV=10^{6} \times 1.6 \times 10^{-19}$ joule
Momentum of photon,
$p=\frac{E}{c}=\frac{1.6 \times 10^{-13}}{3 \times 10^{8}}$
$p=\frac{1.6}{3} \times 10^{-21}=\frac{16}{3} \times 10^{-22}$
$p=5 \times 10^{-22}$ $ kg$ $ m / sec$
Rest mass of photon is zero. But its effective mass is given by
$E=m c^{2}=h v$
$\Rightarrow m=\frac{E}{c^{2}}$
$\therefore$ Momentum of photon, $p=mc=\frac{E}{c^{2}} \times C$
$\Rightarrow p=\frac{E}{c}$
BETA
