The radius of the electron in the first excited state of a hydrogen atom is:

What is the energy associated with the fourth orbit of a hydrogen atom?
$R_H = 2.18 \times 10^{-18} \ J$

Normally,the time taken in an electronic transition is approximately:

For a $H$ atom,the energy transition from $n = 1$ to $n = 2$ is $10.2 \ eV$. What will be the energy for the same transition in $Be^{3+}$ ion?

Bohr's atomic model explains the spectrum of only $.......$.

What is the ratio of the wave number of the first line (lowest energy line) of the Balmer series of the $H$ atomic spectrum to the first line of its Brackett series?