The ratio of the energy of the $He^{+}$ ion in its first and second excited states will be:

As we move away from the nucleus,the energy of the electron

Which of the following equations gives the angular momentum of an electron in a stationary orbit?

If an electron transitions from $n = 5$ to $n = 2$ in a hydrogen spectrum,identify the series and the region of the spectrum.

The total number of spectral lines observed when an electron returns from the $6^{th}$ shell to the $2^{nd}$ shell in a hydrogen atom is:

$A$ source of monochromatic radiation of wavelength $400 \, nm$ provides $1000 \, J$ of energy in $10 \, seconds$. When this radiation falls on the surface of sodium,$x \times 10^{20}$ electrons are ejected per second. Assume that wavelength $400 \, nm$ is sufficient for ejection of electrons from the surface of sodium metal. The value of $x$ is $......$. (Nearest integer) $(h = 6.626 \times 10^{-34} \, Js)$