### What happens when waves hit a boundary?

```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
r i
EXAMPLES

Example 2:
 Find
the angle of reflection

r
EXAMPLES

Example 3:
 Determine
which surface in the diagram the wave
reflects from last and find the angle of reflection
from that surface.
E
i
A
B
D


C
```