Refraction: Bending of light as it passes through a medium. | Reflection: Bouncing of light off a surface.

Angle of Incidence: The angle between the incident ray and the normal. | Angle of Refraction: The angle between the refracted ray and the normal.

Internal Reflection: Some light reflects at the boundary. | Total Internal Reflection: All light reflects at the boundary (occurs when the angle of incidence exceeds the critical angle).

The bending of light as it moves between different materials due to changes in its speed.

A measure of how much light slows down in a material compared to its speed in a vacuum; calculated as n = c/v, where c is the speed of light in a vacuum and v is the speed of light in the medium.

The relationship between the angles of incidence and refraction when light passes between two materials with different refractive indices: $$n_1 sin heta_1 = n_2 sin heta_2$$.

The smallest angle of incidence at which total internal reflection occurs; calculated as $$\theta_{\text{critical}} = \sin^{-1}\left(\frac{n_2}{n_1}\right)$$.

The phenomenon where light is completely reflected back into the original material when it tries to move from a higher index of refraction to a lower one at an angle greater than the critical angle.

The speed of light decreases.

Total internal reflection occurs; the light is completely reflected back into the original medium.

The light passes straight through without bending (no refraction).

The light slows down and bends towards the normal.

The angle of refraction increases, bending away from the normal.