Question

'$n$' photons of wavelength '$\lambda$' are absorbed by a black body of mass '$m$'. The momentum gained by the body is

• A. $\frac{h}{m\lambda }$
• B. $\frac{mnh}{\lambda }$
• C. $\frac{nh}{m\lambda }$
• D. $\frac{nh}{\lambda }$

Answer 1

The correct option is D $\frac{nh}{\lambda }$

As n photons are absorbed by the black body, thus momentum gained by the body is equal to the total momentum of the n photons.

Momentum of one photon $p=\frac{h}{\lambda }$

Thus total momentum of $n$ photons $P=\frac{nh}{\lambda }$