Question

Assertion : Balmer series lies in the visible region of electromagnetic spectrum.
Reason : $\frac{1}{\lambda }=R(\frac{1}{2^2}-\frac{1}{n^2})$

• A. If both Assertion and Reason are true and Reason is the correct explanation of Assertion
• B. If the Assertion and Reason are true but Reason is not correct explanation of Assertion
• C. If Assertion is true but, Reason is false
• D. If Assertion is false but, Reason is true

Answer 1

Answer: (A)

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