Discussion Forum

The refractive index of the material of crystal is 1.68 and that of castor oil is 1.2. When  a ray of  light passes from oil  to glass, its velocity will change by a factor 

Answer:

Explanation:

 We know , refractive index of crystal w.r.t oil,

 $\mu_{co}=\frac{\mu_{c}}{\mu_{o}}$= speed of light in oil/ speed of light in crystal

 where, $\mu_{c}$=  absolute  refractive index of crystal  w.r.t vacuum

    and $\mu_{o}$ = absolute  refractive index of oil w.r.t  vacuum.

 $\mu_{co}=\frac{1.68}{1.2}=\frac{7}{5}$  = speed in oli/ speed in crystal

 Fractional change in velocity ,

 when light travel from oil  to  crystal =  speed in crystal/ speed in oil= $\frac{5}{7}$