The wavelength of sodium `D_2` line obtained from a sodium vapour lamp is ` 5890Å`. If
Channel: Doubtnut
Date: 2020-05-24

The wavelength of sodium `D_2` line obtained from a sodium vapour lamp is ` 5890Å`. If the wavelength of sodium `D_(2)` line emitted by a star is measured as `5895 Å`, then this implies that