Question

The number of spectral lines observed when electron falls from 8th to 2nd energy level is ----
(1) 16
(2) 18
(3) 15
(4) 21​

Answer 1

when electron falls from 8th to 2nd energy level is ----

(1) 16

Answer 2

Answer:

The Correct Answer would be (4) 21. The number of spectral lines observed when an electron falls from the 8th level to 2nd level are 21.

Explanation:

Given: Electrons falling from 8th level to 2nd level.

To Find: Number of spectral lines observed.

Now, we have to find number of spectral lines.

The formula for calculating number of spectral lines if transitions are made between energy levels m and n is :

                                  N = $(\frac{m-n}{2})$ × $(m-n+1)$

where, m,n = energy levels. M is the higher energy level, while n is the smaller. When an electron basically jumps from higher energy level to smaller energy level, it releases energy in the form of spectral lines.

Now, according to question, m = 8 and n = 2. Hence,

N = $(\frac{8-2}{2})(8-2+1)$

    = 3 × 7

 N = 21

Therefore, the number of spectral lines observed when electron falls from 8th to 2nd energy level is 21.