When the frequency of light incident on a metallic plate is doubled,the $KE$ of the emitted photoelectrons will be:

The frequency of a certain line of the Lyman series of the atomic spectrum of the $H$ atom satisfies the following conditions:
$(i)$ It is the sum of the frequency of another Lyman line and a Balmer line.
$(ii)$ It is the sum of the frequency of a certain line,a Lyman line,and a Paschen line.
$(iii)$ It is the sum of the frequency of a Lyman and a Paschen line but no Brackett line.
To what transition does this frequency correspond?

In the Balmer series of the hydrogen atom spectrum,which electronic transition causes the third line?

The maximum energy is possessed by an electron when it is present:

Find out the distance between the $2^{nd}$ and $3^{rd}$ orbit of the $H$-atom $:-$

If the ratio of energies of an electron in the excited states of $H$ and $Li^{2+}$ is $1: 9$,the radius ratio of the electron in the same excited states of $H$ and $Li^{2+}$ is