Refraction Have you ever seen this Refraction of

Refraction

Have you ever seen this?

Refraction of Light n n 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 will bend towards a normal with the boundary.

Sunset is an illusion

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

Law of Refraction (Snell’s Law) n 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 www. sol. sci. uop. edu

Law of Refraction (Snell’s Law) n 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 n 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. www. sol. sci. uop. edu

Continuous Waves – Lower Speed to Higher Speed Note the differences in wavelength and amplitude between of the wave in the two different mediums Incident + Reflected Wave Transmitted Wave v 2 -v 1 Displacement n Boundary Lower speed Higher speed Shorter wavelength Longer wavelength

Continuous Waves – Higher Speed to Lower Speed n Note the differences in wavelength and amplitude between of the wave in the two different mediums Transmitted Wave v 2 Displacement Incident + Reflected Wave -v 1 Boundary Higher speed Lower speed Longer wavelength Shorter wavelength Note: This phenomena is seen with light traveling from air to water.

Speed of Light and the Index of Refraction n n 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 n n 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) n n n Note: Internal reflection can only occur if n 2 < n 1. Internal Reflection Application – fiber optic cable 2 1 1 2 www. micro. magnet. fsu. edu

Refraction of Light http: //www. teachersdomain. org/a sset/lsps 07_vid_lightrefract/ http: //www. teachersdomain. org/a sset/lsps 07_int_refractdemo/