The total number of spectral lines observed when an electron returns from the $6^{th}$ shell to the $2^{nd}$ shell in a hydrogen atom is:

When an electron transitions from the $6^{th}$ orbit to the $2^{nd}$ orbit in a $H$ atom,what is the total number of spectral lines (excluding the Balmer series) produced?

An electromagnetic radiation of wavelength $331.5 \ nm$ is made to strike the surface of a metal. Electrons are emitted with a kinetic energy of $1.2 \times 10^5 \ J \ mol^{-1}$. The work function (in $eV$) of the metal is (given: $h=6.63 \times 10^{-34} \ Js$, $N_{A}=6 \times 10^{23} \ mol^{-1}$, $1 \ eV = 1.6 \times 10^{-19} \ J$)?

Neon gas is generally used in sign boards. If it emits strongly at $616 \, nm$,calculate $(a)$ the frequency of emission,$(b)$ distance traveled by this radiation in $30 \, s$,$(c)$ energy of a quantum,and $(d)$ number of quanta present if it produces $2 \, J$ of energy.

The wave number of the spectral line in the emission spectrum of hydrogen will be equal to $\frac{8}{9}$ times the Rydberg's constant if the electron jumps from

According to Bohr's theory,the angular momentum of an electron in the $5^{th}$ orbit is: (in $, h/\pi$)