Question

The mass of a photon with wavelength 3.6˚A is .

• A. $9.1\times {10}^{-29}kg$
• B. $6.1\times {10}^{-29}kg$
• C. $8\times {10}^{-29}kg$

Answer 1

The correct option is B $6.1\times {10}^{-29}kg$

$Here,\lambda =3.6\times {10}^{-10}m$

We know , de-Broglie wavelength

$\lambda$ = $\frac{h}{p}$ $\Rightarrow$ $\lambda$ = $\frac{h}{mv}$ $\Rightarrow m=$ $\frac{h}{\lambda v}$

Now,

$\lambda =3.6$ $\mathring{A}=3.6\times$ ${10}^{-10}m$

Velocity of photon = Velocity of light

$m=\frac{h}{\lambda v}$ = $\frac{6.626\times {10}^{-34}J{s}^{-1}}{(3.6\times {10}^{-10}m)(3\times {10}^{8}m{s}^{-1})}$

$=6.135\times {10}^{-29}kg$