Number of spectral lines obtained in $He^{+}$ spectra,when an electron makes transition from fifth excited state to first excited state will be

The energy of an electron in the first Bohr orbit of the $H$ atom is $-13.6 \ eV$. The magnitude of the energy value of an electron in the first excited state of $Be^{3+}$ is $.......... \ eV$ $(nearest \ integer \ value)$.

$A$ bulb is rated at $150 \text{ W}$, converting $8\%$ of its energy into light. If the energy of one photon is $4.42 \times 10^{-19} \text{ J}$, how many photons are emitted by the bulb per second?

The work function of sodium metal is $4.41 \times 10^{-19} \ J$. If photons of wavelength $300 \ nm$ are incident on the metal,the kinetic energy of the ejected electrons will be $\left( \dots \right) \times 10^{-21} \ J$. (Given: $h = 6.63 \times 10^{-34} \ J \cdot s; c = 3 \times 10^{8} \ m/s$)

Maximum frequency of emission is obtained for the transition $:-$

The wavelength of the radiation emitted,when in a hydrogen atom an electron falls from infinity to stationary state $n=1$,would be ............... $nm$ (Rydberg constant $= 1.097 \times 10^7 \ m^{-1}$)