$A$ situation of population inversion is related to

The energy $E$ and momentum $p$ of a moving body of mass $m$ are related by a specific equation. Given that $c$ represents the speed of light,identify the correct equation.

The approximate wavelength of a photon of energy $2.48 \,eV$ is ............ $\mathring A$.

The relationship between the velocity and frequency of a photon in a vacuum is represented by a ...... .

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?

Show that the wavelength of electromagnetic radiation is equal to the de Broglie wavelength of its quantum (photon).