Explanation

(c)
We know that,
$E = mc^{2} = \frac{hc}{\lambda}$
$\therefore\ \lambda = \frac{h}{mc}\ \ \ \ or\ m = \frac{h}{\lambda.c}$
where, $\lambda$=wavelength of photon
$h =$Planck’s constant
$m =$mass of photon
$c =$ velocity of light
Given, $\lambda = 3.6\ \mathring{\mathrm{A}} = 3.6 \times 10^{- 10}m$
$\therefore\ \ \ \ \ \ \ m = \frac{6.62 \times 10^{- 34}}{3.6 \times 10^{- 10} \times 3 \times 10^{8}}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = 6.135 \times 10^{- 33}kg$