1. Waves carry energy from one place to another
WAVES: SOUND & LIGHT
Waves carry energy from one place to another 1

2. NATURE OF WAVES
Waves (Def.) – A wave is a disturbance that transfers energy.
Medium – Substance or region through which a wave is transmitted.
Speed of Waves – Depends on the properties of the medium. 2

3. Some waves need help to travel…
Mechanical waves are waves which require a medium.
A medium is a form of matter through which the wave travels (such as water, air, glass, etc.)
Waves such as light, x-rays, and other forms of radiation do not require a medium.

4. What are the two kinds of mechanical waves?
Longitudinal Waves (Compression Waves)
In a longitudinal wave the matter in the wave moves back and forth parallel to the direction of the wave 4

5. What are the two kinds of mechanical waves?
Transverse Waves
In a transverse wave the matter in the wave moves up and down at a right angle to the direction of the wave 5

6. What are the parts of a wave? Transverse wave
The crest is the highest point on a transverse wave.
The trough is the lowest point on a transverse wave.
The rest position of the wave is called the node or nodal line.
The wavelength is the distance from one point on the wave to the next corresponding adjacent point. 6

7. What are the parts of Longitudinal wave
On a compressional wave the area squeezed together is called the compression. The areas spread out are called the rarefaction.
The wavelength is the distance from the center of one compression to the center of the next compression. 7

8. Section 2: Properties of Wave
Chapter 20
Section 2: Properties of Wave

9. Amplitude Related to height of a wave
Max distance the wave vibrates from its rest position (base line)
Larger Amplitude = taller wave= more energy

10. Amplitude

11. Larger Amplitude Means More Energy

12. Wavelength A property of a wave
Distance between any two adjacent crests or compressions in a series of waves
Distance between 2 adjacent troughs or rarefractions
Shorter wavelength = more energy

13. Frequency Number of waves produced in a given time
For longitudinal waves…calculate frequency by counting the # of compressions or rarefractions
For transverse waves…calculate frequency by counting the # of crests or troughs
The slower you go the less times you make waves pass a given point
The faster you go the more times you make waves pass a given point
Units are Hertz (Hz)
1Hz = 1/s (one wave per second)
Higher frequency = more energy

14. Wave Speed Speed at which a wave travels Distance traveled over time
Speed depends on the medium that it’s traveling through

15. Calculating Wave Speed
You need wavelength and frequency
Frequency and wavelength are inversely proportional
V = l (the greek letter lambda) x F (frequency)

16. Chapter 20 Section 3: Wave Interactions

17. Wave Interactions…
Reflection: occurs when a wave bounces back after striking a barrier
All waves can be reflected.
Reflected sound waves are called echoes.
Sunlight is being reflected off of the moon at night.
Water waves reflect off a shoreline.
A wave is transmitted through a substance when it passes through the substance

18. Refraction is the bending of a wave as it passes at an angle from one medium to another.
When a wave moves from one medium to another it changes speed and wavelength
Speed of refraction depends on the medium.

19. Diffraction: the bending of waves around or through an opening
The direction of the wave changes
diffraction depends on wavelength and the size of barrier/opening

20. Interference: the result of 2 or more waves overlapping.
a. constructive interference: increases the amplitude of a wave
b. destructive interference: decreases the amplitude of a wave

21. Constructive Interference
Destructive Interference

22. More on interference waves
Can create standing waves
Standing wave is a wave that forms a stationary pattern in which portions of the wave are at the rest position.
Standing waves have nodes and antinodes.

23. Standing Waves

24. Resonance
Occurs when two objects naturally vibrate at the same frequency
A resonating object absorbs energy from the vibrating object and vibrates too

25. Interference Waves can be deadly!
July 1, Tacoma Bridge Accident