The wavelength of the photon emitted by a hydrogen atom when an electron makes a transition from $n = 2$ to $n = 1$ state is ...... $nm.$

The shortest wavelength of the spectral lines in the Lyman series of the hydrogen spectrum is $915 \text{ Å}$. The longest wavelength of spectral lines in the Balmer series will be: (in $\text{ Å}$)

Taking Rydberg's constant $R_H = 1.097 \times 10^7 \ m^{-1}$,the first and second wavelengths of the Balmer series in the hydrogen spectrum are:

The wavelength of a spectral line emitted by a hydrogen atom in the Balmer series is $\frac{16}{3 R}$ ($R$ is the Rydberg constant). What is the value of the principal quantum number of the state from which the transition takes place?

$A$ $12.5\,eV$ electron beam is used to bombard gaseous hydrogen at room temperature. The number of spectral lines emitted will be:

In the Balmer series,the wavelength of the $2^{\text{nd}}$ line is $\lambda_1$ and for the Paschen series,the wavelength of the $1^{\text{st}}$ line is $\lambda_2$. Then the ratio $\lambda_1 : \lambda_2$ is: