1. Review: The way they move Energy Crest and Trough
What’s the difference between a transverse and longitudinal wave?
What do waves transfer?
What are the high and low points of a transverse wave called?
What are the parts of a longitudinal wave where the particles are spread out and close together?
The way they move
Energy
Crest and Trough
Compression and Rarefaction

2. One wave has one crest and one trough
First thing’s first…
Which of these show ONE full wave?
One wave has one crest and one trough

3. Wavelength Distance What is length a measure of?
So what do you think a wave length is?
The distance between two waves
WAVELENGTH
WAVELENGTH

4. Which has a shorter wavelength?

5. Measuring Wavelength
Does this tell us the distance between the two waves?
Why not?
You have to measure the distance
between two comparable points!
(crest to crest, trough to trough, etc.)

6. Amplitude
The distance between the crest or trough and the wave’s resting position.
Where’s the crest? Trough?
Crest
Amplitude
Resting
Position
Amplitude
Trough

7. Which has a larger amplitude?

8. What does amplitude tell us about a wave?
Which of these waves would cause more damage if it hit the shore?
Which has the larger amplitude?
Which wave has more energy?
THAT’S
AMPLITUDE!

9. We’ve been looking at transverse waves…What about longitudinal?
We can relate all of the parts of a transverse wave to a longitudinal one!

10. We’ll start with wavelength…
In a transverse wave:
But there aren’t any crests or troughs in a longitudinal wave!
The distance from crest to crest or trough to trough
WAVELENGTH
WAVELENGTH

11. So we look at the compressions and rarefactions!
Compressions = Crests
Rarefactions = Troughs
Now we can find the wavelength
Compression to compression
Rarefaction to rarefaction

12. The distance from crest or trough to the wave's resting point
On to amplitude…
In a transverse wave:
We now know that compressions and rarefactions are like the crests and troughs, but it’s hard to find a longitudinal wave’s resting point.
The distance from crest or trough to the wave's resting point

13. Amplitude
For the amplitude of a longitudinal wave, we look at how compressed or how rarefied the spring or particles are.
The more compressed or rarefied it is, the higher the amplitude and vice versa.

14. Frequency
If your friend comes over to your house “frequently”, how often do they come over?
Can you take a guess as to what the “frequency” of a wave is?
The frequency of a wave tells us the number of waves that are produced in a certain amount of time.

15. We need to know how many waves are being produced in 10 seconds.
How can you find the frequency of this wave?
Step 1: pick a point.
Step 2: count the waves that pass that point in 10 seconds.

16. Which has a higher frequency?

17. Which wave did you have to put more energy into to create?
What about Energy?
Waves with
_________________
frequency have
more energy.
a higher
Which wave did you have to put more energy into to create?

18. What is the unit for frequency?
Frequency is measured in Hertz (Hz).
If one full wave passes a point every second, it has a frequency of 1 Hz.
1 wave per second (1 wave/1 sec.)
What is the frequency if three waves pass a point every second?
3 Hz. (3 waves/1 second)
What is the frequency if six waves pass a point every three seconds?
2 Hz. (6 waves/3 seconds)

19. Wave Speed A B There are two ways to calculate wave speed.
Option 1: time how long a wave takes to get from point A to point B. A B

20. Option 2: Use the following formula
Wave speed = wavelength x frequency
Wave Speed =
8 meters/second
Wavelength – 2 meters
Frequency –
4 Hz.
(4 waves pass every second)

21. Wave speed is affected by several factors
The type of wave
Example: electromagnetic waves always travel at the same speed in a vacuum (300,000 km/s – the speed of light)
The medium the wave is moving through
If you start two waves in a pan, one with water and one with corn syrup, which will reach the other side of the pan first?
Another example is popping your knuckles underwater as opposed to above water.

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

23. Image position You think in straight lines!
The image is located behind the mirror.

24. Refraction Which direction does it bend as it slows?
Sudden change in direction of a wave as it changes speed.
It must enter obliquely to change direction!
Which direction does it bend as it slows?

25. Refraction
In both cases the speed of the wave has decreased. This is indicated by the decrease in wavelength!

26. Refraction
In which medium does light travel faster? (glass rod appears bent)

27. Refraction
In simple terms, refraction is caused when a wave moves from one type of medium to another that has a different density. This makes objects between them look different.