Wednesday, October 5, 2011

Physics Form 4: Chapter 5 - Reflection of Light on Plane Mirror

  • Reflection involves a change in direction of the light ray.
  •  The ray of light approaching the mirror is known as incident ray.
  • The light ray that leaves the mirror is known as reflected ray.
  • The angle of incidence is the angle between normal line and the incident ray.
  • The angle of reflection is the angle between normal line and the reflected ray.

If the reflecting surface is very smooth, the reflection of light that occurs is called specular or regular reflection. The laws of reflection are as follows:
  1. The incident ray, the reflected ray and the normal to the reflection surface at the point of the incidence lie in the same plane.
  2. The angle of incidence is equal to angle of reflection.
  3. The reflected ray and the incident ray are on the opposite sides of the normal.

Ray Diagram

Characteristic of image formed

  • Virtual
  • Upright
  • Laterally inverted
  • Same size as the object
  • As far behind the mirror as the object is in front of it.

Uses of ray diagram
Six students - Al, Bo, Cy, Di, Ed, and Fred sit in front of a plane mirror and attempt to see each other in the mirror. Whom can Al see?

Al could see any student positioned between Ed and Fred by looking at any other positions along the mirror. However in this case, there are no other students between Ed and Fred; thus, Ed and Fred are the only students whom Al can see.


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