Question

For the same angle of incidence, the angle of refraction in three media A,B,and C are 15,25 and respectively. In which medium is the velocity of light is minimum..??

Answer 1

μ = refractive index = speed of light in vacuum / speed of light in medium = c / v
  = sin i / sin r

v = c sin r / sin i

v is minimum for the medium having the least r.
If the angles of refraction are 15, 25, and angle > 25,  then speed is minimum for the medium with r = 15 deg.