The mass of a photon with a wavelength equal to 1.54x 10^-8cm is

$\text{ We know that }\mathrm{\lambda }=\frac{\mathrm{h}}{\mathrm{mv}};\therefore \mathrm{m}=\frac{\mathrm{h}}{\mathrm{\lambda v}}$
$\text{ The velocity of photon }\left(\mathrm{v}\right)=3\times {10}^8{\mathrm{msec}}^{-1}$
$\lambda =1.54\times {10}^{-8}\mathrm{cm}=1.54\times {10}^{-10}\text{ meter }$
$\therefore \mathrm{m}=\frac{6.626\times {10}^{-34}\mathrm{Js}}{1.54\times {10}^{-10}\mathrm{m}\times 3\times {10}^8{\mathrm{msec}}^{-1}}$
$=1.4285\times {10}^{-32}\mathrm{kg}$