The wavelength (in $\mathring{A}$) of a photon having energy $3 \ eV$ is approximately.
$1 \ eV = 1.6 \times 10^{-12} \ erg$
$h = 6.626 \times 10^{-27} \ erg \ s$
$c = 3 \times 10^{10} \ cm/s$

$A$ metal surface is exposed to solar radiation.

The photoelectric effect shows:

Consider a helium $(He)$ atom that absorbs a photon of wavelength $330 \ nm$. The change in the velocity (in $cm \ s^{-1}$) of the $He$ atom after the photon absorption is . . . . . .
(Assume: Momentum is conserved when the photon is absorbed. Use: Planck constant $= 6.6 \times 10^{-34} \ J \ s$,Avogadro number $= 6 \times 10^{23} \ mol^{-1}$,Molar mass of $He = 4 \ g \ mol^{-1}$)

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

The Vividh Bharati station of All India Radio,Delhi,broadcasts on a frequency of $1368 \, kHz$ (kilo hertz). Calculate the wavelength of the electromagnetic radiation emitted by the transmitter. Which part of the electromagnetic spectrum does it belong to?