The Compton effect demonstrates that .....

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 we express the energy of a photon in $KeV$ and the wavelength in $\mathring{A}$,then the energy of a photon can be calculated from the relation:

In pair annihilation,an electron and a positron destroy each other to produce gamma radiation. How is the momentum conserved?

The energy of a quantum of frequency $10^{15} \ Hz$ and $h = 6.6 \times 10^{-34} \ J \cdot s$ will be:

The number of photons per second on an average emitted by a source of monochromatic light of wavelength $600 \, nm$,when it delivers a power of $3.3 \times 10^{-3} \, W$,is: $(h = 6.6 \times 10^{-34} \, Js)$