Reflection – Learn
We observe examples of waves being reflected everyday: the reflection of a sound wave causes an echo, your reflection in the mirror is the reflection of a light wave and water waves reflecting off a wall. Airport controllers also use radar (the reflection of radio and microwaves) to track planes.
We often use incident and reflected rays to illustrate reflection diagrams. These rays represent the direction that the wave is travelling. The actual wave is a series of wave fronts that are perpendicular to the direction that the wave is travelling:
Reflection off a smooth surface: We can represent the reflection of waves off a smooth surface as illustrated below:
- The law of reflection states that the angle of incidence is equal to the angle of reflection.
- The angle of incidence is the angle between the ray coming onto the surface (the incident ray) and the normal to the surface.
- The angle of reflection is the angle between the ray reflected away from the surface (the reflected ray) and the normal to the surface.
- The normal line is a line that is perpendicular to the reflecting surface.
Reflection off a curved surface: The reflection of waves off curved surfaces is useful for car headlights and satellite dishes. We can represent the reflection of waves off a curved surface as illustrated below. Note that the reflected rays all meet at a position known as the focal point.