05 – The Law Of Reflection

What happens when waves hit a boundary? When water waves strike a barrier straight on, they reflect back along the same path.

What happens when waves hit a boundary? When incident waves strike a parabolic surface, the waves reflect to a focal point.

What happens when waves hit a boundary at an angle? When incident waves strike a barrier at an angle they reflect off at the same angle. The Normal (N) is a line drawn perpendicular to the barrier/surface the wave hits. The normal line intersects the surface at the identical point the wave hits the barrier/surface. The Angle of Incidence, θi , of a wave is the angle measured from the incident wave (i) to a line normal to the barrier/surface. The Angle of Reflection, θr , of a wave is the angle measured between the reflected wave (r) and a line normal to the barrier/surface.

The Law of Reflection The Angle of Incidence is equal to the Angle of Reflection

EXAMPLES Example 1: Find the angle of reflection

Examples Example 2: Find the angle of reflection

Examples Example 3: Determine which surface in the diagram the wave reflects from last and find the angle of reflection from that surface.