Reflection & refraction of light

Created by :KHOIRUL SOLEHAH BINTI

ABDUL RAHIM

REFLECTION• Reflection is the change in direction of a wavefront at an interface

between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. Mirrors exhibit specular

reflection.

REFRACTION• Bending LightIf you have ever half-submerged a straight stick into water, you have probably noticed that the stick

appears bent at the point it enters the water (see Figure 1.) This optical effect is due to refraction. As light passes from one transparent medium to another, it changes speed, and bends. How much this happens depends on the refractive index of the mediums and the angle between the light ray and the line perpendicular (normal) to the surface separating the two mediums (medium/medium interface) (See Figures 2a and 2b.) Each medium has a different refractive index (see list below.) The angle between the light ray and the normal as it leaves a medium is called the angle of incidence. The angle between the light ray and the normal as it enters a medium is called the angle of refraction.

• Snell's LawIn 1621, a Dutch physicist named Willebrord Snell (1591-1626), derived the relationship between the

different angles of light as it passes from one transperent medium to another. When light passes from one transparent medium to another, it bends according to Snell's law which states:

Ni * Sin(Ai) = Nr * Sin(Ar),where:

Ni is the refractive index of the medium the light is leaving,Ai is the incident angle between the light ray and the normal to the meduim to medium interface,Nr is the refractive index of the medium the light is entering,Ar is the refractive angle between the light ray and the normal to the meduim to medium interface.