Question:
The wavelength of an X-ray beam is $10 \AA$. The mass of a fictitious particle having the same energy as that of the $X$ - ray photons is $\frac{x}{3} h \mathrm{~kg}$. The value of $x$ is
Solution:
(10)
Given wavelength of an $x$-ray beam =10 A
$\because E=\frac{h c}{\lambda}=m c^{2}$\
$m=\frac{h}{c \lambda}$
The mass of a fictitious particle having the same energy as that of the $x$-ray photons $=\frac{x}{3}$ hkg
$\frac{x}{3} h=\frac{h}{c \lambda}$
$x=\frac{3}{c \lambda}$
$=\frac{3}{3 \times 10^{8} \times 10 \times 10^{-10}}$
$x=10$
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