Question

Assertion : Balmer series lies in the visible region of electromagnetic spectrum.
Reason : $\frac{1}{\lambda }=R\left[\frac{1}{2^2}-\frac{1}{n^2}\right]$ where $n=3,4,5$.

• A. If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
• B. If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
• C. If the Assertion is correct but Reason is incorrect.
• D. If the Assertion is incorrect and Reason is correct.

Answer 1

Answer: (A)

The wavelength in Balmer series is given by
$\frac{1}{\lambda }=R\left[\frac{1}{2^2}-\frac{1}{n^2}\right],n=3,4,5,\dots \dots$
$\frac{1}{{\lambda }_{\max }}=R\left[\frac{1}{2^2}-\frac{1}{3^2}\right]$
${\lambda }_{\max }=\frac{36}{5R}=\frac{36}{5\times 1.097\times 10^7}=6563\mathring{A}$
and $\frac{1}{{\lambda }_{\min }}=R\left[\frac{1}{2^2}-\frac{1}{{\infty }^2}\right]$
${\lambda }_{\min }=\frac{4}{R}=\frac{36}{1.097\times 10^7}=3646\mathring{A}$
The wavelength $6563\mathring{A}$ and $3646\mathring{A}$ lie in visible region. Therefore, Balmer series lies in visible region.