Question

Assertion In Lyman series of H-spectra, the maximum wavelength of lines is $121.65nm$.
Reason Wavelength is maximum if there is transition from the very next level.

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

Answer 1

Answer: (A)

$\frac{1}{\lambda }=R_H{Z}^2\left[\frac{1}{n_1^2}-\frac{1}{n_2^2}\right]$
For Lyman series, $n_1=1$
and $n_2=2$
$[\because$ for maximum $\lambda$, transition is from very next level.]
$\therefore \frac{1}{\lambda }=109678\times (1{)}^2\left[\frac{1}{(1{)}^2}-\frac{1}{(2{)}^2}\right]c{m}^{-1}$
or $=\frac{109678\times 3}{4}c{m}^{-1}$
$\lambda =\frac{4\times 10^7\times 10^{-7}}{3\times 109678}cm$
$=121.65nm$