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

$A$ photon in motion has a mass.

$A$ light bulb emits $5\%$ of its energy as visible light. How many quanta are emitted per second by a $100 \ W$ lamp? (Assume the wavelength of visible light is $5.6 \times 10^{-5} \ cm$)

$A$ gamma ray photon creates an electron-positron pair. If the rest mass energy of an electron is $0.5\, MeV$ and the total kinetic energy $(K.E.)$ of the electron-positron pair is $0.78\, MeV$,then the energy of the gamma ray photon must be.......$MeV$.

The radiation with frequency $1.0 \times 10^{14} \ Hz$ lies in the infrared region. The energy of one photon of this radiation in joules is:

What is called as the quantum of energy? What is its energy?