1. Properties of Waves

2. Announcement
We will have a lab session on Wednesday. Please come to the middle school physics lab instead.

3. Goal of the class
To understand transverse and longitudinal waves. To understand wave motion and particle vibrations.
Question of the Day: How do we calculate the velocity of a wave?
Previous Answer: They are related by the formula:
Previous question: How are time period (T) and frequency (f) related?

4. Wave Motion What happens when you drop a stone in the water?
If there is a leaf next to the place you drop the stone, what happens to its motion?
The stone creates ripples in the water.
The leaf will rise up and down, but it won’t move away from its original location.
From this we can tell a lot about the particles in the water.
The particles in the water travel locally, but they don’t move across the surface of the pond.

5. Wave Motion In this example the water is the medium.
Most form of waves require a medium to travel through, such as sound waves.
Sound waves cannot travel through outer space (which is something that is often depicted incorrectly in Hollywood movies).
Medium: A physical environment through which a disturbance can travel.
Waves thar require a medium are called mechanical waves.
Some waves don’t require a medium, such as Electromagnetic waves, light and such

6. Wave Types
We can demonstrate the two main waves using a long coiled spring.
There are 2 main waves, transverse and longitudinal.
Transverse waves look like sine waves. Oscillating like SHM around the central point.

7. Wave Types
Transverse waves oscillate perpendicular to the direction of travel.
Longitudinal waves oscillate parallel to the direction of travel.
Draw waves for each!

8. Wave Types
Draw waves for each!

9. Period, Frequency and Speed
Practice problem: A piano string tuned to middle C vibrates with a frequency of 262 Hz. Assuming the speed of sound in air is 343 m/s, calculate the wavelength produced by the string.
Add on labels for the equation on the board.
The speed in which a wave front moves at can be found usnig the formula
V=f x lambda
Start with v=d/t but for a wave d= lambda and t = time period
F=1/T and sub in
V = f lambda
Wavelength = 1.31m

10. Homework
Read chapter 11 – Sections 3
Questions on P394 Q23, 34, 35