An angle of refraction is the angle between the refracted ray and the o incident ray.
o normal.
O medium.
O boundary

b) normal

Explanation:

The angle of refraction (transmission) Θt is the angle between the refracted ray and the normal N'. 2. When a light ray hits a surface normally, the angle between the incident ray and the normal is 0, so Θi = 0. Since the angle of reflection equals the angle of incidence, Θr= 0.

mass and volume are the answers you are looking for