Laws of Reflection of Light

Suppose a ray of light (IO) falls on a reflecting surface AB at O, after reflection it goes along OR. The reflection of light from the surface takes place according to the following two laws.

  1. Incident ray, reflected ray and the normal at the point of incidence, all lie in the same plane.

  2. The angle of incidence is equal to the angle of reflection: ∠i = ∠r.

During reflection, there is no change in speed, frequency and wavelength of light.

Reflection of light may be classified as regular reflection and diffused reflection.

Regular Reflection

When reflecting surface is very smooth and the rays of light falling on it are reflected straight off it, then it is called regular reflection.

Diffused Reflection

When the reflection of light takes place from rough surface the light is reflected off in all directions.

When surface is rough, parallel incident rays do not reflect parallel. In diffused reflection due to roughness of the surface normal drawn at the point of incidence of parallel incident rays are not parallel, hence the reflected rays reflect in all direction but obey the laws of reflection.