Question

A spectroscopic instrument can resolve two nearby wavelengths λ and λ + Δλ if λ/Δλ is smaller than 8000. This is used to study the spectral lines of the Balmer series of hydrogen. Approximately how many lines will be resolved by the instrument?

Answer 1

The range of wavelength falling in Balmer series is between 656.3 nm and 365 nm.

It is given that the resolution of the instrument is λ/ (λ + ∆λ) < 8000.

Number of wavelengths in this range will be calculated in the following way:

`(656.3-365)/8000 = 36`

Two lines will be extra for the first and last wavelength.

∴ Total number of lines = 36 + 2 = 38