If the emitted radiation falls in the microwave region,the device is termed as

$A$ proton moving with a momentum $p_{1}$ has a kinetic energy $1/8$th of its rest mass-energy. Another light photon having energy equal to the kinetic energy of the proton possesses a momentum $p_{2}$. Then,the ratio $\frac{p_{1}-p_{2}}{p_{1}}$ is equal to

There are materials which absorb photons of shorter wavelength and emit photons of longer wavelength. Can there be stable substances which absorb photons of larger wavelength and emit light of shorter wavelength?

If the energy of a photon is expressed in units of $KeV$ and the wavelength in units of $\mathring{A}$,then the energy of the photon can be calculated by:

Assertion: The energy $(E)$ and momentum $(p)$ of a photon are related by $p = E/c$.
Reason: The photon behaves like a particle.

What is the charge on a photon?