What is the radius of Bohr's fifth orbit for $B^{+4}$ in $\mathring{A}$ (in $.645$)?

The hydrogen spectrum consists of several spectral lines in the Lyman series ($L_1, L_2, L_3 \ldots$; $L_1$ has the lowest energy among the Lyman series). Similarly,it consists of several spectral lines in the Balmer series ($B_1, B_2, B_3 \ldots$; $B_1$ has the lowest energy among the Balmer lines). The energy of $L_1$ is $x$ times the energy of $B_1$. The value of $x$ is . . . . . . $\times 10^{-1}$ (Nearest integer).

For a hydrogen atom,the energy of the $n^{th}$ orbit is given by the equation $E \propto n^y$. What is the value of $y$?

State the uses of atomic spectra.

The dual nature of photons is described by:

Suppose the ionization energy of a hydrogen-like species is $960 \ eV$. The value of the principal quantum number for an energy level of $-60 \ eV$ will be $......$.