Reflection and Ray Model of Light
A light ray will be reflected from a smooth surface in such a manner that the angle incident ray makes normal to the reflecting surface at the point of incidence which is precisely equal to the angle that the reflected ray makes with normal. Also, the reflected ray along with the incident ray and the normal to the reflecting surface all lie on the same plane defined at the incident point and it shows θi=θr.
The optical ability of humans and other animals is the consequence of the complex interaction of light, eyes and brain. People are able to see because light from an object can move through space and influence our eyes. When light reaches our eyes, signals are sent to our gray matter, and our brain deciphers the information in order to perceive the appearance, location and movement of the objects we are looking at. If a ray of light could be witnessed approaching and reflecting off of a flat mirror, then the manner of the lights reflection would follow a predictable law known as the law of reflection.
The ray model is extremely useful while studying reflection of light, refraction of light and various images created by lenses, spherical mirrors and plane mirrors.
If the reflection takes place from a perfect plane surface, then we term it as regular reflection. The reflected light has larger intensity in a particular direction and negligible intensity in all other directions.
If the reflection takes place from an irregular or rough surface the regular feature of light is not observed and although at every point the light ray gets reflected the overall effect observed is basically cancellation and overlapping of all reflected rays resulting in a diffused reflection.
Some Examples on Reflection and Ray Model of Light
Problem 1: Angle of incident for a plane mirror at the point of incidence is perceived to be 48 degrees with the normal. What is the angle of reflection?
(at the point of incident with normal) Angle of incidence = angle of reflection
Thus, angle of reflection = 48 degrees (with normal)
Problem 2: The angle of reflection with the normal at the point of incident is perceived to be 108 degrees. What is the angle of incidence?
Angle of incidence = angle of reflection
Thus, angle of incidence = 108 degrees (with normal)