Question

Rays of light moving upward through water toward the water–air boundary at angles larger than 488 to the nor- mal are totally reflected. No rays larger than 488 refract outside. How about the reverse? Is there an angle at which light rays in air meeting the air–water boundary will totally reflect? Or will some light be refracted at all angles?

Answer 1

Answer:

N1*sin(theta1)= n2*sin(theta2) says Snells Law.

The air refraction index is around 1 and the water refraction index is about 1.33.  The angle of refraction must be greater than 90 degrees to be fully reflected.

Then 1*sin(theta1)= 1.33*sin(90)= 1.33* 1= 1.33 There is no angle with a sin greater than 1.  And light coming in at any angle will be refracted greater than 90 degrees and it will not be fully reflected internally moving from air to water— absolute internal refraction can only occur when it comes to a higher refractive index to a lower one.