Number of visible lines when an electron returns from 5 th orbit to ground state in $\mathrm{H}$ spectrum :

In the $\mathrm{H}$spectrum, there are 10 lines that are visible when an electron returns from the fifth orbit to the ground state.

The total number of spectral lines is $=\frac{n(n-1)}{2}$.

The quantity of spectral lines is $=\frac{5(5-1)}{2}=10$

The $\mathrm{UV}$area has these lines.

Lyman series changes to level $\mathrm{n}=1$ are represented by these series.