1. Waves

2. Waves do NOT carry matter
Disturbances
All waves carry energy
Waves displace matter
Waves do NOT carry matter

3. Medium Medium – the material a wave travels through
When sound travels through air, the air is the medium
When sound travels through a solid, such as glass, the glass is the medium

4. Types of Waves

5. Transverse Waves
Examples: water waves, light waves, waves in a string or a rope, secondary seismic waves
Displace the medium perpendicular to the direction the wave travels

6. Crest
Wavelength
amplitude
Trough

7. Longitudinal Waves (compression waves)
Example: sound waves, primary seismic waves
Displace the medium parallel to the direction the wave is moving

8.
(Wave animation)

9. amplitude
compression
wavelength
rarefaction

10. Wave Interactions

11. Reflection A wave “bounces back” when it encounters a new medium
Law of reflection: the angle of reflection equals the angle of incidence

12. Reflection Reflection from a fixed boundary
Reflection from a soft boundary

13. Some Uses of Reflection
Mirrors
Communications
Radar
Sonar

14. Refraction
A wave changes speed and direction (bends) when it enters a new medium
Waves travel at different speeds in different mediums (due to density differences)
When a wave strikes the boundary between mediums at an angle, one part of the wave slows down before another, and the wave bends
Refraction animation -

15.
Light reflected from fish is bent as it travels from water into the air.
To the viewer, it appears as if the fish is along a straight line (the refracted ray)

16. Diffraction A wave bends as it passes around a barrier
Used in spectroscopy (learning about the universe from the colors of light emitted from objects)

17. Interference Two or more waves combine
Because waves are not matter (they are disturbances that displace matter), more than one wave can occupy the same space at the same time
This is called superposition

18. Interference (continued)
When two crests meet, their amplitudes are added (constructive interference)
When a crest and a trough meet, their amplitudes cancel each other out (destructive interference)
The resulting wave is the sum of the amplitudes at all points

19. Constructive and Destructive Interference

20. Superposition of Waves

21. Constructive and Destructive Interference