Question

Let '$p$' and '$E$' denote the linear momentum and energy of emitted photon respectively. If the wavelength of incident radiation is increased ___________.

• A. Both $p$ and $E$ increase
• B. $p$ increases and $E$ decreases
• C. $p$ decreases and $E$ increases
• D. Both $p$ and $E$ decrease

Answer 1

The correct option is D Both $p$ and $E$ decrease

Energy of photon $E=\frac{hc}{\lambda }$

$⟹$ $E\propto \frac{1}{\lambda }$

Hence energy of photon decreases as the wavelength of light increases.

Also, momentum of the photon $p=\frac{E}{c}$

$⟹$ $p\propto E$

Thus momentum of photon also decreases as its energy decreases.

Hence option D is correct.