Refraction

Have you ever seen this?

Refraction of Light When light travels through a surface between two different media, the light will be refracted if the angle of incidence is greater than zero. If light is passing into a more dense media, it willbend towards a normal with the boundary.

Sunset is an illusion

Light Passing Through Glass θ1θ1 θ4θ4 θ3θ3 θ2θ2 Incident Ray Reflected Ray Refracted Ray Air Glass Note:  1 =  4  2 =  3 The light exiting the glass is parallel to the light entering it.

Law of Refraction (Snell’s Law) The ratio of the sine of the angle of incidence to the angle of refraction is a constant. n 1 sin 1 = n 2 sin 2 Where: n 1, n 2 = index of refraction  1 = Angle of incidence  2 = Angle of refraction

Law of Refraction (Snell’s Law) The ratio of the sine of the angle of incidence to the angle of refraction is a constant. n 1 sin 1 = n 2 sin 2 Where: n 1, n 2 = index of refraction  1 = Angle of incidence  2 = Angle of refraction Note, the incident ray will always bend towards the normal when transitioning from a material with a lower index of refraction to one with a higher index of refraction.

Incident + Reflected Wave Lower speed Shorter wavelength Higher speed Longer wavelength Transmitted Wave -v 1 v2v2 v1v1 Continuous Waves – Lower Speed to Higher Speed Note the differences in wavelength and amplitude between of the wave in the two different mediums Boundary

Higher speed Longer wavelength Lower speed Shorter wavelength Continuous Waves – Higher Speed to Lower Speed Note the differences in wavelength and amplitude between of the wave in the two different mediums Displacement Boundary Incident + Reflected Wave Transmitted Wave v1v1 v2v2 -v 1 Note: This phenomena is seen with light traveling from air to water.

Speed of Light and the Index of Refraction The index of refraction, by definition, is the ratio of the speed of light in a vacuum to the speed of light in a substance. The index of refraction is always greater than 1.

Total Internal Reflection When the angle of incidence is such that the angle of refraction is equal to 90 o, the critical angle ( c ) has been attained. All rays will be reflected internally at all angles greater than this angle.  c = sin -1 (n 2 /n 1 ) Note: Internal reflection can only occur if n 2 < n 1. Internal Reflection Application – fiber optic cable

Refraction of Light sset/lsps07_vid_lightrefract/ sset/lsps07_int_refractdemo/