The ratio of the energy of a photon of $2000 \ \mathring{A}$ wavelength radiation to that of $4000 \ \mathring{A}$ radiation is

The energy of an electron in the first Bohr orbit of $H$ atom is $-13.6 \ eV$. The energy value of an electron in the first excited state of $Li^{2+}$ is ............... $eV$.

Calculate the energy associated with the third orbit of $He^{+}$.

If $m$ and $e$ are the mass and charge of the revolving electron in the orbit of radius $r$ for a hydrogen atom,the total energy of the revolving electron will be:

The wavelength of radiation emitted when an electron falls from the $4^{th}$ Bohr orbit to the $2^{nd}$ in an $H$ atom is .............. $nm$.

$A$ bulb emits light of wavelength $4500 \ \mathring{A}$. The bulb is rated at $150 \ \text{W}$ and $8\%$ of the energy is emitted as light. How many photons are emitted by the bulb per second?