The momentum of a photon of energy $1 \text{ MeV}$ in $\text{kg-m/s}$ will be

$A$ 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 $c = 3 \times 10^8 \ m/s$)

$A$ 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.

If a photon has velocity $c$ and frequency $\nu$,then which of the following represents its wavelength?

Monochromatic light of wavelength $667 \, nm$ is produced by a helium-neon laser. The power emitted is $9 \, mW$. The number of photons arriving per second on average at a target irradiated by this beam is:

The average number of photons emitted per second by a laser of power $6.6 \times 10^{-3} \,W$ producing light of wavelength $600 \,nm$ is (Planck's constant,$h = 6.6 \times 10^{-34} \,J \cdot s$):