What is the charge on $\gamma$-rays?

Calculate the wavelength,frequency and wave number of a light wave whose period is $2.0 \times 10^{-10} \,s$.

Consider two radiations of wavelengths $1. \lambda_1 = 2000 \mathring{A}$ and $2. \lambda_2 = 6000 \mathring{A}$. The ratio of the energies of these two radiations $\left(\frac{E_1}{E_2}\right)$ is . . . . . . (Nearest integer).

The frequency of a radio wave from Mars to Earth is $6 \times 10^3 \, s^{-1}$. If the distance between them is $8 \times 10^7 \, km$,how much time will it take?

What is the photoelectric effect? Explain it.

Which one of the following frequencies of radiation (in $Hz$) has a wavelength of $600 \ nm$?