Wavefronts are lines connecting points that are in phase when waves spread. Rays show the direction of wave motion. Reflection occurs when waves bounce off a surface, which can be regular or diffuse. The law of reflection states that the angle of incidence equals the angle of reflection when measuring from the normal line perpendicular to the surface. When a wave passes between different mediums, its velocity and direction change due to refraction as described by Snell's law.

1. Wave properties
Wavefront – a line joining
points that are in phase
- the lines you see
when ripples spread on
water are wavefronts
Rays – arrows
drawn to show the
direction of wave
motion

2. Reflection
- The bouncing of
waves off a surface
Regular reflection –
reflection from a smooth
surface
- an image would
appear to be coming from
behind the surface

3. Diffuse reflection –
reflection from a non-
smooth surface
- light bounces off
the surface but no image
can be seen
When light hits a surface, part of the wave is reflected,
part is absorbed by the atoms of the material.
When light hits a transparent material, some is
transmitted through the window.

4. Law of reflection
The angle of incidence equals the
angle of reflection
All angles are measured to the
normal line (perpendicular to the
surface)

5. Refraction
When a wave passes from one medium into
another, its velocity changes. If the wave hits the
boundary at an angle, the wave also changes
direction.

7. Light travels at 2 x 108 m/s in a substance. What is its
index of refraction?
The index of refraction of a liquid is 0.80. How fast
does light travel in it?

8. Snell’s Law

9. A water wave travelling at 20 m/s enters a shallow
region where its velocity is 15 m/s. If the angle of
incidence of the water wave is 50o, what is the
angle of refraction?
35.2o

10. Light travelling through air is incident on the
surface of a pool of water at an angle of 40o.
Calculate the angle of refraction.