1. Characteristics of Waves

2. Waves at a Boundary
The speed of a wave depends on the medium that the wave is travelling through
When a wave travels from one medium to another; some energy is transferred to the new medium, while some energy is reflected back

3. Waves at a Boundary The TRANSMITTED wave is ALWAYS UPRIGHT
The REFLECTED wave can be upright or inverted

4. Waves at boundary rules!
When the pulse travels from a less dense medium to a more dense medium, the reflected pulse is upside down and
The velocity of the wave and its wavelength decrease (think of the universal wave equation)

5. Waves at boundary rules!
When the pulse travels from a more dense medium to a less dense medium, the reflected pulse is upright
The velocity of the wave and its wavelength increase.

6. Diffraction
Diffraction is the spreading out of waves as they pass through a small opening or go around obstacles

7. Diffraction
The amount of diffraction (bending of the wave) is dependant on the size of the opening and the wavelength of the wave:
The smaller the opening, the greater the diffraction
The longer the wavelength, the greater the diffraction

8. Interference of Waves
The Principle of Superposition: When there are two wave sources in a medium, the two waves combine to form a resultant wave that is the algebraic sum of the two waves
This “sum” of the waves will produce interference patterns

9. Types of Interference Constructive Interference:
Destructive Interference:
When a crest meets a crest, their energies combine (also when a trough meets a trough)
When a crest and trough meet, their energies cancel out

10. Interference Patterns with Diffraction
The crest and trough pass through each other, only having an effect where they meet
You can observe this interference if you put two point sources in water
The pattern you would see is called an interference pattern

11. Interference and Diffraction

12. A few definitions…
Anti-nodal Lines: where waves meet to form constructive interference (crest and crest or trough and trough)
Nodal – Lines: where waves meet to form destructive interference (crest and trough)

13. Homework
p. 166 front & back