the change of direction of a ray of light as it passes obliquely from one medium into another of different transmission speed

When light travels from a less dense to more dense medium (light slows down), the ray is refracted toward the normal. Example: light slows down when it passes from air into water air water n i r i>r

When light travels from a more dense medium to a less dense medium (light speeds up), the ray is refracted away from the normal. Example: light speeds up when passing from glass into air air glass n i r i < r

An object’s ability to decrease the speed of light, and therefore cause refraction, is given by its index of refraction. By definition: the index of refraction of any transparent substance is equal to the speed of light in a vacuum divided by the speed of light in that substance. n = c / v n = (3 x 108 m/s) / v

angles of incidence and refraction The angles of incidence and refraction are related in such a way that n = (sin i)/(sin r), where i = angle of incidence and r = angle of refraction vacuum whenever light passes from a vacuum into the substance. In general, for light passing from medium 1 into medium 2, n1 sin 1 = n2 sin 2 This relationship is known as Snell’s Law. Snell’s Law n1n1 n2n2 11 22

Total Internal Reflection may occur when light enters a new medium and speeds up (bends away from the normal). Investigate here. here The maximum angle of incidence in which light may enter air from another substance and not undergo total internal refraction is known as the critical angle, and is related to the index of refraction of the substance by: sin c = 1/n

Click here, here, Click here, here,here and here to view and here to viewhere simulations of Snell’s simulations of Snell’s Law. Law. View an analytical derivation of the geometrical relationship here. here Investigate total internal reflection here. here