The rest mass of the photon is

If sources of ultraviolet $(\lambda \approx 400 \ nm)$,visible $(\lambda \sim 550 \ nm)$,and infrared $(\lambda \sim 700 \ nm)$ radiation each have a power rating of $100 \ W$,then the number of photons emitted per unit area per unit time is maximum for:

The energy of a photon of visible light with the maximum wavelength in $eV$ is approximately .......

The idea of the quantum nature of light has emerged in an attempt to explain:

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

What is the momentum of a photon with a frequency of $10^9 \ Hz$?