1. WAVES
WAVE INTERACTIONS

2. FOUR WAYS WAVES INTERACT
REFLECTION
REFRACTION
DIFFRACTION
INTERFERENCE
How waves interact with a medium
How waves interact with other waves

3. LAW OF REFLECTION
Angle of incidence = angle of reflection

4. We see from where we think the light ray is coming.
Reversed image
Non-reversed image

5. 29.2 The Law of Reflection
Incident rays and reflected rays make equal angles with a line perpendicular to the surface, called the normal.
The angle between the incident ray and the normal is the angle of incidence.
The angle between the reflected ray and the normal is the angle of reflection.
Angle of incidence = Angle of reflection 5

6. Ordinary paper has a rough surface when viewed with a microscope.
29.4 Diffuse Reflection
Diffuse reflection allows us to see most things around us.
Light is diffusely reflected from paper in many directions.
Light incident on a smooth mirror is only reflected in one direction.
Ordinary paper has a rough surface when viewed with a microscope. 6

7. 29.8 Refraction of Light
As a light wave passes from air into water, its speed decreases. 7

8. CONCAVE AND CONVEX MIRRORS
Convex mirror causes light rays to converge.
Concave mirror causes light rays to diverge.

9. REFLECTION
The bouncing back of a wave when it meets a surface or boundary.

10. REFRACTION
The bending of a wave as it passes from one medium to another.
Light from pencil moves from air to your eye, through water and glass to your eye, through plastic to your eye

11. DIFFRACTION
The bending of a wave as it passes through an opening or by an edge.
Ex.: Hear a voice from around the corner.

13. 31.1 Diffraction and Huygens’ Principle
The extent to which the water waves bend depends on the size of the opening. 13

14. Using diffraction gratings

15. INTERFERENCE
The combination of two or more waves that exist in the same place at the same time.
Constructive Interference (additive effect—in phase)
Destructive Interference (subtractive effect—out of phase)