a) Incident ray - PE
An incident ray is a ray of light that strikes a surface. The angle between this ray and the perpendicular or normal to the surface is the angle of incidence.
b) Refracted ray - EF
A refracted ray is a ray which has entered a medium and bent either away from the normal or towards the normal depending on the density of the new medium in comparison to the old one.
c) Emergent ray - FS
The emergent ray is the ray of light which passes through a denser medium(glass) to a rarer medium(air).
d) Angle of refraction - ∠r
Angle of refraction is defined as the angle between the normal and the refracted ray.
e) Angle of deviation - ∠D
The angle of deviation through a triangular prism is defined as the angle between the incident ray and the emerging ray.
f) Angle of emergence - ∠e
Angle of emergence is defined as the angle between the normal and the emergent ray.