The largest wavelength in the ultraviolet region of the hydrogen spectrum is `122` nm. The smallest wavelength in the infrared region of the hydrogen spectrum (to the nearest integer) is

Options

A. `802 nm`
B. `823 nm`
C. `1882 nm`
D. `1648 nm`

Answer

B

Explanation

The series in `uv` region is Lyman series. Longest wavelength corresponds to minimum energy which occurs in transition from `n=2` to `n=1`.
`:. 122(1//R)/((1)/(1^(2))-(1)/(2^(2)))`.......(1)
The smallest wavelength in the infrared region corresponds to maximum energy of Paschen series
`lambda=(1//R)/((1)/(3^(2))-(1)/(oo))`.....(2)
from (1) and (2) `lambda=823.5 nm.`