Light enters a substance from air at 30 degrees to thenormal.
it continues through the substance at 23 degrees tothe normal. what
would be the critical angle for thissubstance?

Explanation:

The angle of incidence and refraction are both measured from the normal

angle of incidence = 30°

angle of refraction = 23°

refractive index(n) = sini / sinr

n = sin30°/sin23°

n = 1.27965

refractive index (n) = 1/sinC

where C is the critical angle.

sinC= 1/n

C =arcsin (1/n)

C =arcsin (1/1.27965)

C = 51.39°