1. What Are Some Properties of Waves
Unit E, Chapter 4, Section 1 pE

2. Waves
Wave: disturbance that travels through matter or space, carrying energy from one place to another without carrying matter with it
Information we receive travels in waves
Light, sound, radio, televisions,
Mechanical waves: waves that need matter to travel through
Substance, matter, only vibrates back & forth or side-to-side
Floating object
Bobs up and down
Doesn’t move in direction of waves
Waves don’t transport matter, they only transport energy

3. Waves
Surface waves in water = combination of motion of two kinds of waves
Back and forth vibration
Side-to-side vibration
Resulting motion is circular

4. Waves Crest: highest part of wave Trough: lowest part of wave
Height: vertical distance between crest and trough
Amplitude: distance any point on wave is moved from resting position
Equal to ½ height
Greater energy of wave, greater amplitude
Measured from resting position to crest or trough

5. Waves Wavelength: horizontal distance between one crest and the next
Always the same in a series of waves
Can be measured between any two identical points
Amplitude and wavelength of waves can vary greatly

6. Different Kinds of Waves
Transverse wave: particles vibrate at right angles to direction of wave
Yarn moved side-to-side
Waves traveled forward
Examples:
Guitar string
Light (Electromagnetic waves)
Light doesn’t need a medium, matter, to travel through

7. Different Kinds of Waves
Longitudinal wave: particles vibrate back and forth in the same direction as the wave is moving
Compressions: areas where particles are closer together
Rarefaction: areas where particles are spread out
Examples:
Sound waves
Most other waves that travel through liquids or gases

8. Speed, Frequency, and Wavelength
The speed of a wave is always the same in a particular substance, unless there are changes to the substance
Speed of sound through air always the same
Change temperature – speed changes
Speed of waves through water always the same
Change depth – speed changes
Speed measured by measuring distance a single point, crest or compression, travels in given time

9. Speed, Frequency, and Wavelength
Frequency: number of vibrations a wave has in a given time
Measured by counting number of crests or compressions passing point in certain amount of time
Measured in units called hertz
1 hertz = 1 vibration per second
1 crest passes a point in 1 second
2 hertz = 2 crests passing in 1 second

10. Speed, Frequency, and Wavelength
Relationship:
Speed = wavelength x frequency
Increase frequency, wavelength decreases
Faster you sent waves down spring, shorter distance between waves

11. Energy From Waves
All waves carry energy in the form of: light, sound, heat, or motion
Life on Earth depends on waves carrying energy from sun
Heats planet
Allowing plants to make food

12. Energy From Waves People use energy carried in waves Solar panels
Change sun’s light energy into heat or electricity
Ocean waves
Scientists doing experiments to use energy
Advantages:
Renewable source
Won’t cause pollution from combution

13. Energy From Waves Energy in waves can also destroy Hurricane waves
Huge amounts of energy
Cause almost as much damage as winds
Tsunami: waves generated by undersea earthquakes
“Tidal waves”
Carry greatest amount of energy
Begins on ocean floor
On surface it not very noticeable
When it reaches shore, height may be 35 m (115 ft)

14. Energy From Waves Energy in waves can also destroy Earthquakes
Seismic waves
Energy travels through Earth
Both transverse and longitudinal
Third kind of wave on surface, similar to water
Ground ripples up and down
Circular motion

15. Summary
Mechanical waves are disturbances in a substance that carry energy without carrying the substance (matter)
Other waves, i.e. light, carry energy without needing matter to travel through
Transverse waves displace particles at right angles to the motion of the wave
Longitudinal waves displace particles in the same direction as the wave
Relationship – speed = wavelength x frequency
Some energy from waves can be used, but the energy in waves can also cause great damage

16. Homework Read Unit E, Chapter 4, Section 1, pE108-113
Answer ?s on Google Form or WS