Question

what is the relation between angle of incidence, angle of refraction and angle of emergence.

Answer 1

Refraction is the bending of the path of a light wave as it passes across the boundary separating two media. Refraction is caused by the change in speed experienced by a wave when it changes medium.

The angle of incidence is the angle between a ray incident on a surface and the line perpendicular to the surface at the point of incidence, called the normal. The ray can be formed by any wave: optical, acoustic, microwave, X-ray and so on. In the figure above, the red line representing a ray makes an angle θ with the normal (dotted line). The angle of incidence at which light is first totally internally reflected is known as the critical angle. The angle of reflection and angle of refraction are other angles related to beams.

The angle of emergence is the angle of the light coming out of a medium (for an example a glass slab with parallel sides). The first medium could be air and the medium in the middle could be water or a glass slab with parallel sides. The ray of light travels down at an angle through the air and enters the glass. The light refracts or bends as it enters the glass, then carries on and emerges at a new angle back into the air. The ray of light coming out is parallel to the incident ray and the angle of emergence is the same as the angle of incidence.

Answer 2

a - angle of incidence, b - angle of refraction, c - angle of emergence
n1, n2 - refractive indexes
sina/sinb=n2/n1
a=c if ray go through a prism with parallel sides