The ratio of the time period of an electron in the first and third orbit of an $H$-atom would be:

$A$ metal having a work function of $4 \, eV$ is exposed to a photon of $\lambda = 1240 \, \mathring{A}$. If an accelerating potential of $7.6 \, V$ is applied,then the electron with maximum kinetic energy will have a speed equal to -

If the radius of the first orbit of a hydrogen-like ion is $1.763 \times 10^{-2} \ nm$, the energy associated with that orbit (in $J$) is

The figure shows six spectral lines in an emission spectrum arising from energy level transitions. Which of the following spectral lines does not appear in the absorption spectrum?

The wavelength of a spectral line for an electronic transition is inversely related to

Maximum number of spectral lines possible when an electron jumps from $5^{th}$ excited state to ground state in a sample containing only one Hydrogen atom will be