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

The energy of one mole of photons of radiation of frequency $2 \times 10^{12} \ Hz$ in $J \ mol^{-1}$ is $.....$ (Nearest integer) (Given: $h = 6.626 \times 10^{-34} \ Js$,$N_A = 6.022 \times 10^{23} \ mol^{-1}$)

Which one of the following corresponds to a photon of highest energy?

Which of the following is $NOT$ a property of $X$-rays?

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?

The frequency of a radio station of All India Radio is $1368 \, kHz$. The wavelength of the electromagnetic waves emitted by the transmitter is ............... $m$.