An electron changes its position from orbit n = 4 to the orbit n = 2 of an atom. The wavelength of the emitted radiation’s is (R = Rydberg’s constant)

$\frac{16}{R}$ $\frac{16}{3 R}$ $\frac{16}{5 R}$ $\frac{16}{7 R}$

$\frac{16}{3 R}$

$\frac{1}{\lambda}=R\left[\frac{1}{n_1^2}-\frac{1}{n_2^2}\right]=R\left[\frac{1}{(2)^2}-\frac{1}{(4)^2}\right] \Rightarrow \lambda=\frac{16}{3 R}$