Question

An electron makes a transition from orbit n = 4 to the orbit n = 2 of a hydrogen atom. The wave number of the emitted radiations (R = Rydberg's constant) will be.

• A. $\frac{16}{3R}$
• B. $\frac{2R}{16}$
• C. $\frac{3R}{16}$
• D. $\frac{4R}{16}$

Answer 1

Answer: (C)

$\frac{3R}{16}$

Answer 2

Wave number

$\frac{1}{\lambda} = R\left\lbrack \frac{1}{n_{1}^{2}} - \frac{1}{n_{2}^{2}} \right\rbrack = R\left\lbrack \frac{1}{4} - \frac{1}{16} \right\rbrack = \frac{3R}{16}$.