In a hydrogen atom,the binding energy of the electron in the $n^{th}$ state is $E_n$. Then,the frequency of revolution of the electron in the $n^{th}$ orbit is:

The electric potential between a proton and an electron is given by $V = V_0 \ln(r/r_0)$,where $r_0$ is a constant. Assuming Bohr's model to be applicable,find the variation of $r_n$ with $n$,where $n$ is the principal quantum number.

$A$ $\mu$-meson of charge '$e$',mass $208 m_e$ moves in a circular orbit around a heavy nucleus having charge $+3e$. The quantum state '$n$' for which the radius of the orbit is the same as that of the first Bohr orbit for a hydrogen atom is [approximately]:

For principal quantum number $n = 3$,the possible values of orbital quantum number $l$ are

The kinetic energy of the electron in an orbit of radius $r$ in a hydrogen atom is proportional to ($e=$ electronic charge).

In a hydrogen atom,an electron makes a transition from the $5^{\text{th}}$ orbit to the $3^{\text{rd}}$ orbit. The change in the angular momentum for this electron is . . . . . . .