Aray of light traveling in air strikes the surface of a liquid. if the angle of incidence is 29.7◦ and the angle of refraction is 16.3◦ , find the critical angle for light traveling from the liquid back into the air. answer in units of ◦

When light moves from a medium with higher refractive index to a medium with lower refractive index, the critical angle is the angle above which there is no refracted ray, and it is given by:
(2)
where  is the refractive index of the second medium and  is the refractive index of the first medium.

We can find the ratio by using Snell's law:
(1)
where
is the angle of incidence
is the angle of refraction

By using the data of the problem and re-arranging (1), we find


and if we use eq.(2) we can now find the value of the critical angle: