Bohr’s model of atom explains :

The most probable radius (in $pm$) for finding the electron in $He^{+}$ is

Typical electronic energy gaps in molecules are about $1.0 \ eV$. In terms of temperature,the gap is closest to

For the $H$ spectrum,the limiting line in the $Balmer$ series has a frequency of ...... $(R_\infty = 3.29 \times 10^{15} \text{ cycles/s})$

If the electron of a hydrogen atom is present in the first orbit, the total energy of the electron is

If $\lambda_0$ and $\lambda$ are respectively the threshold wavelength and wavelength of incident light,the velocity of photoelectrons ejected from the metal surface is