the wave equation superposition diffraction

1. The wave Equation and
Superposition
7.3

2. The Wave Equation - Revision
TEXT: Page 240

3. Same Frequency Different wavelength?
An implication of the wave equation that is worth noting is that a
source that has a specific frequency of vibration is able to produce
waves of different wavelengths, depending upon the medium that
carries the wave.
Q) What does this mean about the difference of the speed of
sound in air and water?
A) If the same frequency is producing a longer wavelength
this must mean that the wave is travelling further between
pulses. A greater distance in the same time would mean a
greater speed.

4. Example Problem

5. Waves meeting barriers
• https://www.youtube.com/watch?v=6T82rOyytGU
• https://www.youtube.com/watch?v=YQHbRw_hyz4

6. Waves meeting barriers
Fixed End Free End
This means that the peak of the wave has moved half a
wavelength from where it would have been. The peak is now
where the trough was and the trough is now at the peak (The
peak and trough are half a wavelength away from each other).
NOW LETS DO IT WITH THE SLINKY!!
TIE BOB’S SHOE LACE TO ONE END OF THE SLINKY TO REPRESENT A FREE END

7. Superposition
• https://www.youtube.com/watch?v=BWraEDaVXZM

8. Superposition

9. Superposition – Constructive interference
Constructive interference
occurs when two waves
meet that have particle
displacements in the same
direction.

10. Superposition – Destructive interference
Destructive interference
occurs when two waves
meet that have particle
displacements in
opposite
directions.

11. Superposition – Both Types

12. Diffraction!

13. Diffraction!
We have seen how a wave can spread out from
a point source, but waves are also capable of
bending around obstacles or spreading out
after they pass through a narrow gap. This
bending of the direction of travel of a wave is
called DIFFRACTION.

14. Summary