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?

Electromagnetic radiation with maximum wavelength is

The radiation is emitted when a hydrogen atom goes from a high energy state to a lower energy state. The wavelength of one line in the visible region of the atomic spectrum of hydrogen is $6.5 \times 10^{-7} \, m$. The energy difference between the two states is:

Which parameter is indicated by the number of waves passing through a given point in one second?

Which of the following series of emission spectral lines for hydrogen is observed in the visible region?

The energies $E_1$ and $E_2$ of two radiations are $25 \ eV$ and $50 \ eV$ respectively. The relation between their wavelengths,i.e.,$\lambda_1$ and $\lambda_2$,will be: