The electron in a hydrogen atom undergoes a transition from higher orbits to an orbit of radius $476.1 \text{ pm}$. This transition corresponds to which of the following series?

The ratio of the maximum wavelengths of the Lyman and Balmer series is ....

Light of frequency $1.6 \times 10^{16} \ Hz$ falling on a metal plate emits electrons that have double the kinetic energy compared to the kinetic energy of electrons emitted when light of frequency $1.0 \times 10^{16} \ Hz$ falls on the same plate. The threshold frequency $(v_0)$ of the metal in $Hz$ is:

Which of the following corresponds to the energy of a possible excited state of hydrogen (in $eV$)?

The energy of a photon is calculated by ......

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