Question

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

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

Answer 1

Answer: (D)

$\frac{1}{\lambda }=R_H{Z}^2\left[\frac{1}{n_1^2}-\frac{1}{n_2^2}\right]$ 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 $=\frac{109678\times 3}{4}c{m}^{-1}$ $\lambda =\frac{4\times {10}^7\times {10}^{-7}}{3\times 109678}cm=121.65nm.$