Question

An X-ray photon of wavelength $\lambda$ and frequency $v$ collides with an electron and bounces off. If ${\lambda }^{\prime }$ and $v^{\prime }$ are respectively the wavelength and frequency of the scattered photon, then

• A. ${\lambda }^{\prime }=\lambda ;v^{\prime }=v$
• B. ${\lambda }^{\prime }<\lambda ;v^{\prime }>v$
• C. ${\lambda }^{\prime }>\lambda ;v^{\prime }>v$
• D. ${\lambda }^{\prime }>\lambda ;v^{\prime }<v$

Answer 1

The correct option is D

${\lambda }^{\prime }>\lambda ;v^{\prime }<v$

Due to the collision, the energy of the scattered photon will be less than that of the incident photon as some energy is lost in the collision.
Now, $E=hv=\frac{hc}{\lambda }$
Thus, if $E$ decreases, $v$ decreases and $\lambda$ increases and the correct choice is (d).