light refraction questions

[MYS9]

A light ray traveling through a glass medium, index of refraction1.52, is incident on the boundary between the glass and water, index of refraction 1.33 What is the critical angle for the glass at this boundary? What would the critical angle be if the incident medium was air instead of water?

would i use snell's law? how?

thanks

[Chi Meson]

Yes, Snell's law. The critical angle only exists for a wave that is going from the slow medium to the fast medium. The critical angle is the angle of incidence that causes the angle of refraction to be exactly 90 degrees. Set up the formula using "theta 2" as 90 and solve for "theta 1."