question_answer

The deviation is maximum for which colour:

A)  violet             

B)  red

C)  blue              

D)  green

Correct Answer: A

Solution :

Since wavelength of violet light is minimum and that of red light is maximum. \[\therefore \] \[{{\lambda }_{R}}>{{\lambda }_{V}}\] From Cauchy's dispersion \[\mu \,\alpha \,\frac{1}{\lambda }\] Hence, \[{{\mu }_{v}}>{{\mu }_{g}},\] i.e., refractive index of glass for violet light is maximum. Therefore, from the formula, \[{{\delta }_{m}}=(\mu -1)A.\]. Where \[{{\delta }_{m}}\] is angle of deviation and A the angle of prism, violet light deviates the most and red the least.