A spectrograph's trihedral prism is manufactured from glass whose refractive
Channel: Doubtnut
Date: 2020-08-23

A spectrograph's trihedral prism is manufactured from glass whose refractive index varies with wavelength as `n = A + B//lambda^(2)`, where `A` and `B` are constats, with `B` being equal to `0.010mum^(2)`. Making use of the formula from the foregoing problem, find: (a) how the resolving power of the prism depends on `lambda`, calculate the value of `lambda//delta lambda` in the vicinity of `lambda_(1) = 434nm` and `lambda_(2) = 656nm` if the width of the prism's base is `b = 5.0 cm`,  (b) the width of the prism's base capacble of resolving the yellow doublet of sodium `(589.0` and `589.6nm`).