The radius of a hydrogen atom in the ground state is $0.53 \ Å$. After collision with an electron,it is found to have a radius of $2.12 \ Å$. The principal quantum number $n$ of the final state of the atom is:

In a hydrogen atom,an electron transitions from an orbit of radius $R$ to an orbit of radius $4R$. What is the ratio of their time periods?

In a hydrogen atom,if $r_n$ is the radius of the $n^{th}$ orbit and $L_n$ is the orbital angular momentum,then which of the following relations is correct?

The electron in a hydrogen atom makes a transition $n_1 \rightarrow n_2$,where $n_1$ and $n_2$ are the principal quantum numbers of the two states. Assume the Bohr model to be valid. The frequency of orbital motion of the electron in the initial state is $1/27$ of that in the final state. The possible values of $n_1$ and $n_2$ are

If the atom $_{100}Fm^{257}$ follows the Bohr model and the radius of the outermost shell of $_{100}Fm^{257}$ is $n$ times the Bohr radius,then find $n$.

The de-Broglie wavelength of the electron in the first Bohr orbit of the hydrogen atom is