The critical angle for a substance is measured at 53.7 degrees. light enters from air at 45.0 degrees. at what angle it will continue?

When light travels from a medium with greater refractive index  to a medium with smaller refractive index , there exists an angle (called critical angle) above which the light is totally reflected, and the value of this angle is given by

In this problem, we know that the critical angle is, so we can find the ratio between the refractive indices of the two mediums:

and since the second medium is air (n=1.00), the refractive index of the first medium is


In the second part of the problem, we have light entering from air () at angle of incidence of , into the second medium with . By using Snell's law, we can find the angle of refraction of the light inside the medium:

therefore, the efficiency is: