In the hydrogen spectrum,if an electron transitions from the $6^{th}$ orbit to the $2^{nd}$ orbit through multiple steps,the number of spectral lines produced is ....

What is the angular momentum of an electron in the fourth orbit of a hydrogen atom?

What is the hydrogen spectrum? Give its characteristics.

$A$ $124 \ W$ bulb converts only $15 \ \%$ of the energy supplied to it into visible light of wavelength $640 \ \text{nm}$. How many photons are emitted by the light bulb in one second?

If the energies of two light radiations $E_1$ and $E_2$ are $25 \ eV$ and $100 \ eV$ respectively,then their respective wavelengths $\lambda_1$ and $\lambda_2$ would be in the ratio $\lambda_1: \lambda_2=$

In Bohr's atomic model,the radius $(r)$ and energy $(E)$ of an orbit $(n)$ are related as: