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
$\frac{1}{\lambda}=R\left[\frac{1}{2^2}-\frac{1}{n^2}\right], n=3,4,5, \ldots \ldots$
$\frac{1}{\lambda_{\max }}=R\left[\frac{1}{2^2}-\frac{1}{3^2}\right] $
$\lambda_{\max }=\frac{36}{5 R}=\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.