Question

why does a light of a particular colour whose angle of deviation from path of incidence is less has higher speed?

Answer 1

The refractive index of a particular colour depends on the deviation by the relationnλ=sin(A+D2)sin(A/2)and refractive index is related to the velocity by the relationn=c/vTherefore lesser deviation colour will be having more speed.$$\begin{gathered} Therefractiveindexofaparticularcolourdependsonthedeviationbytherelation \\ {n}_{\lambda }=\frac{{\displaystyle \frac{}{}}\sin \left({\displaystyle \frac{A+D}{2}}\right)}{\sin (A/2)}andrefractiveindexisrelatedtothevelocity \\ bytherelation \\ n=c/v \\ Thereforelesserdeviationcolourwillbefasterinspeed. \end{gathered}$$