1. Waves
Check your notes!

2. What is a wave? According to the “standards” it is
A way for energy to be carried from one place to another without transferring the material.
Please check your definitions:
A mechanical wave is a disturbance that travels through a medium from one place to another.
A disturbance can be a vibration or wiggle.
A medium is a material: solid, liquid, or gas
Please list 3 examples of mechanical waves

3. Anatomy of a Wave λ Crest is the top of a wave
Trough is the bottom of a wave
Equilibrium position is the resting position when there are no disturbances
Amplitude is the magnitude of the disturbance from equilibrium
A → the units depend on whether you’re talking about sound waves, water waves, or light
wavelength is the distance between adjacent peaks or troughs in a wave
λ → wavelength (m) λ
crest A
equilibrium position
trough

4. Wavelength Practice Draw the wave below on your paper
Count how many waves you drew
Measure the amplitude
Measure the wavelength of the wave

5. Frequency velocity is how fast the wave is moving
v → velocity (m/s)
frequency is the number of waves or oscillations each second.
An oscillation is when something swings back and forth
f → frequency units (1/s) or hertz (hz)
If the 93 bus comes 10 times in an hour, what is the frequency?
Example: If two waves pass by in 1 s then what is the frequency? v

6. Period
period is the time it takes for one wave to pass or one oscillation.
T → period units (s)
Example: What is the period of a wave when you observe that two waves pass by in 1 s?
The period (T) and frequency (f) are inversely related

7. Practice Problems
In a large room, a sound wave traveling from a violin produces a tone with a frequency of 264 Hz. The speed of sound in the room is 340 m/s. What is the wavelength of the sound?
The velocity of sound in a particular gas is 900 m/s. A sound wave propagating in the material has a wavelength of 15 m. What is the frequency of the sound?

8. The Wave Equation The velocity equation: v = fλ
As the frequency increases, what happens to the wavelength?
Velocity of a wave does not change when the frequency or wavelength changes
Frequency
Wavelength
Velocity

9. Demonstration
Let’s make some waves!

10. Mechanical Wave Types There are two types of mechanical waves:
Transverse waves: when the particles in the wave moves perpendicular to the direction of the waves motion and energy transport.
The wave moves forward
slinky particles move up and down

11. slinky particles move back and forth
Mechanical Wave Types
Longitudinal waves: when the particles of the wave move parallel to the direction of motion and energy transport.
The wave moves forward
slinky particles move back and forth

12. Label each wave below as longitudinal or transverse and explain your choice
Tsunami (giant wave of water) → _______________
Earthquake → _____________
Sound → ____________
Jump rope → _______________
Draw the waves A and B below in your notebook
Which wave has a longer wavelength? Why?
Which wave has a larger amplitude? Why? A B

13. Slinky Lab
Purpose: to see how the velocity, frequency, and wavelength are related
Hypothesis: answer the following in your notebook
What do you think happens to the wavelength of a wave as the frequency increases or decreases?
What do you think happens to the velocity of a wave as the frequency changes?

14. Procedures Make a table to record your data
Create a wave using the slinky and record the following information for your wave
# of swings in 10 s, you should calculate the frequency using this information
Measure and record the wavelength
Create a smaller wave and then repeat steps A and B above
# of swings in 10 s
frequency
wavelength
Wave 1
Wave 2

15. Frequency and Wavelength
From your observations, how are the frequency and wavelength related? Fill in the table
Frequency
Wavelength ↓ ↑

16. Molecular Movement

17. Analysis Wavelength (m) Frequency (hz) Wave 1 Wave 2
Plot your data on two separate graphs.
What does the area of your graph tell you? Look at the units!

18. The Wave Equation Frequency Wavelength Velocity Frequency Wavelength

19. Practice Classifying Waves

20. Waves Travelling in a Medium
Why do we call them mechanical waves?
How can we change a waves velocity faster?
Do waves travel fastest in a gas, liquid, or solid?
Do waves travel slowest in a gas, liquid, or solid?