Question

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

• A. Both assertion and reason are true and reason is the correct explanation of assertion
• B. Both assertion and reason are true but reason is not the correct explanation of assertion
• C. Assertion is true but reason is false
• D. Both assertion and reason are false

Answer 1

Answer: (A)

The wavelength in Balmer series is given by
$\frac{1}{\lambda }=R[\frac{1}{2^2}-\frac{1}{n^2}],n=3,4,5,....$
$\frac{1}{{\lambda }_{max}}=R[\frac{1}{2^2}-\frac{1}{3^2}]$
$\frac{1}{{\lambda }_{max}}=\frac{36}{5R}=\frac{36}{5\times 1.097\times 10^7}=6563\mathring{A}$
and $\frac{1}{{\lambda }_{min}}=R[\frac{1}{2^2}-\frac{1}{{\infty }^2}]$
${\lambda }_{min}=\frac{4}{R}=\frac{4}{1.097\times 10^7}=3646\mathring{A}$
The wavelength $6563\mathring{A}and3646\mathring{A}$ lie in visible region.
Therefore, Balmer series lies in visible region.