Question

Total number of spectral lines when electron jumps from $8^{th}$ orbit to $2^{nd}$ orbit is:

• A. $6$
• B. $36$
• C. $21$
• D. $38$

Answer 1

Answer: (C)

$21$

Is electron falls from orbit $n_2$ to $n_1$ then the number of spectral lines emitted is given by,

$N_E=\frac{(n_2-n_1+1)\times (n_2-n_1)}{2}$

Now, $n_2=8$ to $n_1=2$

$N_E=21$