Question

How many spectral line will be observed when an electron jumps from n = 5 to n = 1 in the visible line spectra of H spectrum?

• A. 10
• B. 3
• C. 6
• D. 8

Answer 1

The correct option is B 3

Given: Transition in H -spectra where $n_1$ = 1 and $n_2$ = 5.
We know, Total number of spectral line = $\frac{(n_2-n_1)(n_2-n_1+1)}{2}$
So, total number of lines = $\frac{(5-1)(5-1+1)}{2}$ = 10
The 10 transitions possible are $5\to 4$, $5\to 3$, $5\to 2$, $5\to 1$, $4\to 3$, $4\to 2$, $4\to 1$, $3\to 2$, $3\to 1$, $2\to 1$.
Now, transitions in visible regions are when electron jumps from $5\to 2$, $4\to 2$, $3\to 2$ i.e. in the visible region.
Three spectral lines will be obtained in the line spectrum.