1. -Standing Waves -Law of Reflection -Diffraction -Interference of Waves
Physics
Mr. Berman

2. Standing Wave

3. Standing Waves Nodes: zero displacement
Antinodes: maximum displacement

4. Forming a Standing Wave on a Rope
Incident pulse interferes with the reflected (inverted) pulse.

5. How is a standing wave formed?
Incident pulse Reflected pulse Standing wave

6. Wave on a String
(Applet)

7. Standing Waves Applet

8. L= 1/2 λ L= λ L= 1 1/2 λ L= 2 λ L=2 1/2 λ L=3 λ

9. Natural Frequencies of a Stretched String (Fixed Ends)
Fundamental Frequency
First Harmonic

10. Problem
A string of length 1m vibrates. The speed of the wave in the material is 400m/s.
Calculate the first three natural frequencies and draw the corresponding standing waves.
Answer: 200Hz, 400Hz, 600Hz
200, 400, 600 Hz

11. Law of Reflection
The angle of incidence equals the angle of reflection.

12. Refraction
When a wave crosses a boundary between two different media, the wave changes direction because it changes velocity.
Frequency is constant (as emitted from source)
Velocity change is a result of wavelength change

13. Refraction

15. Why do ocean waves approach the beach parallel to the shore?
Where is the speed greater?
Hint: check the wavelength

16. Diffraction The bending of waves around a small obstacle or hole.
The smaller the wavelength the smaller the diffraction.

17. One Wave Two Waves Interfering