The magnetic moment of an electron due to its orbital motion is proportional to ($n$ = principal quantum number).

Radius of the second Bohr orbit of a singly ionized helium atom is ......... $ \mathring A $

$A$ moving Hydrogen atom makes a head-on collision with a stationary Hydrogen atom. Before the collision,both atoms are in the ground state,and after the collision,they move together. The minimum kinetic energy of the moving Hydrogen atom,such that one of the atoms reaches the excitation state,is (in $eV$)

In a hydrogen atom,if $V_n$ and $V_p$ are the orbital velocities in the $n^{\text{th}}$ and $p^{\text{th}}$ orbits respectively,then the ratio $V_p : V_n$ is:

The orbital acceleration of an electron is .........

The ratio of centripetal acceleration for an electron revolving in $3^{rd}$ and $5^{th}$ Bohr orbit of hydrogen atom is