$A$ photon of frequency $f$ has a momentum associated with it. If $c$ is the velocity of light,the momentum is:

$A$ blue lamp emits light of mean wavelength $4500 \ \text{Å}$. The lamp is rated at $150 \ \text{W}$ and $8 \%$ efficiency. Calculate the number of photons emitted by the lamp per second.

$A$ lamp of power $942 \ W$ radiates energy uniformly in all directions. The wavelength of radiation is $660 \ nm$. The photon flux on a small screen $5.0 \ m$ from the lamp in units of $\frac{\text{photon}}{m^2 \cdot s}$ is (Take Planck's constant $h = 6.6 \times 10^{-34} \ J \cdot s$ and speed of light $c = 3 \times 10^8 \ m/s$)

The rest mass energy of an electron is $0.54 \, MeV$. If the velocity of the electron is $0.8 \, c$,then the kinetic energy $(K.E.)$ of the electron is .......... $MeV$.

Write the equation for the energy of a photon.

The momentum of a photon of energy $h\nu$ will be: