When a ray of light passes from an optically more dense medium into a less dense medium, the majority of the light is refracted away from the normal, but a small amount is reflected from the boundary.
• This can be investigate in the laboratory using a semi-circular glass block.
• If the angle of incidence in the more dense medium increase, the angle of refraction also increases until at the critical angle, the angle of refraction is 90 degrees.
• If the angle of incidence in the glass is further increased, all of the light is reflected from the boundary. This means that the ray has undergone total internal reflection.
• The value of the critical angle depends upon the medium on either side of the boundary. The critical angle for glass is 42 degrees and the critical angle for water is 49 degrees.
• The critical angle for a particular medium is related to its refrective index by this equation:
Using total internal reflection
• T.I.R is used in periscopes because the light rays will hit the boundary of the glass and reflect at…