In the following ray diagram, calculate the speed of light in the liquid of unknown refractive index.
Consider an incident angle (angle between normal and ray)as a critical angle and it's alternative angle is also equal to critical angle.
Clearly,
Sin i = 30/ √(30)^2 +(40)^2
=30/50 =3/5
Refractive index of liquid =1/sin i
=5/3
Also,
Refractive index of liquid= speed of light in air/
speed of light in the liquid
5/3=3*10^8/v
V= 3/5*3*10^8
V=1.8 *10^8