1. Sound Waves and Electromagnetic Waves

2. Georgia Performance Standards
SPS9. Students will investigate the properties of waves.
a. Recognize that all waves transfer energy.
b. Relate frequency and wavelength to the energy of different types of electromagnetic waves and mechanical waves.
c. Compare and contrast the characteristics of electromagnetic and mechanical (sound) waves.
d. Investigate the phenomena of reflection, refraction, interference, and diffraction.
e. Relate the speed of sound to different mediums.
f. Explain the Doppler Effect in terms of everyday interactions.

3. What is a wave?
A rhythmic disturbance that transfers energy through matter or space.
The wave exists only as long as it has energy to carry
When a wave hits a boat, does it carry the boat along? Explain. NO, the matter (water) moves up and down, the wave moves horizontally.

4. What is the source of a wave?
Vibrations cause waves.
Vibrations are REPEATING DISTURBANCES.
When an object vibrates, it is moving, therefore it has energy which is given off to a nearby particle causing them to vibrate as well.

5. Mechanical Waves
Some waves must have substance to travel through and some do not.
Mechanical Waves must have a material to travel through (vibrate the particles).
Sound waves, ocean waves, waves on a rope are mechanical waves.
The material that waves travel through is called the medium.
Mediums:
Sound waves travel through solids,
liquids or gas.
Ocean waves travel through water.

6. Parts of a Wave
IN A MECHANICAL WAVE,
Amplitude shows how much energy a wave has.
y-axis
x-axis
If a sound wave has very little amplitude, the sound would be
Like a whisper or soft.

7. Parts of a wave Wavelength is measured from crest to crest or
or trough to trough
1 wave=
A complete
crest
and a
complete
trough
Wavelength is measured in meters.
The crest is the highest point of a wave. The trough is the
Lowest point of wave.

8. Frequency of Waves
Frequency is the number of waves that cross a point in a given amount of time.
Measured in Hertz
1 Hertz = 1 wave/sec A.
Which has a higher frequency?
A or B? a B.
Which has a higher amplitude?
A or B? they are the same
Which has a greater wavelength?
A or B? B

9. Calculate frequency
1 wave consists of 1 crest + 1 trough freq= # waves/ time it takes to pass a point
6 seconds here
Frequency = 3.5 waves/ 6 sec = .58 Hz

10. Types of Waves
Transverse Waves: waves where the matter in the medium moves back and forth at right angles to the direction that the wave travels
Has crests and troughs
2. Compressional Waves: a type of wave where the matter in the medium moves back and forth in the same direction that the wave travels.
Has compressions and rarefactions
Also called Longitudinal waves

11. Compression Wave
What is a rarefaction? Molecules spread out in a compression wave
What is a compression? Molecules compressed (squished together) in
compression wave

12. Transverse Waves vs Compressional Waves
Examples of Transverse waves:
Electromagnetic waves
Ocean waves
Wave on a rope
Examples of Compressional Waves:
1. Sound waves
transverse
compressional

13. Transverse or Compressional?
Label,
Wavelength,
Amplitude,
Crest and
Trough 
______________
_______________
rarefactions
compression
rarefactions
compression

14. INTERFERENCE
Interference occurs when two (or more) waves are traveling through the same medium at the same time and interact.

15. Constructive Interference
When two waves combine to form in a way that it produces a larger wave.
Crest of one wave meets crest of another wave (or trough meets trough)
Larger wave 

16. Destructive Interference
When two waves interact in a way that forms a smaller wave.
When the crest of one wave meets the trough of another wave
Example:
Noise cancelling
headphones

17. Wave Behaviors
Reflection: when a wave strikes an object and bounces back.
Examples: Mirror Image and Echoes
Reverberation below… bouncing
Off walls and getting louder…
(reflected sound wave)

18. Reflection of Waves Echolocation…. (Reflected sound)
SONAR… Sound Navigation and Ranging
(reflected sound wave)
RADAR…. RAdio Detection And Range (reflected Ewave)
Seeing Colors (reflected Ewaves)

19. Wave Interactions 2. Refraction: the bending of a
wave caused by a change in
speed due to a change in
medium.
Examples: pencil looks bent in
water, rainbow

20. Interaction of Waves
3. Diffraction: occurs when an object causes a wave to change direction and bends around it.
Light
Sound

21. Electromagnetic Waves
Created by vibrating electric charges
Can travel through a vacuum (needs NO medium to travel through)
Have a wide variety
of frequencies and
wavelengths.
People can only
see the wavelengths
around 400 nanometers
to 700 nanometers.
All travel at the speed of
light in a vacuum
300,000 km/s
670, 617, 000 mi/hr

22. Electromagnetic Spectrum
A device for organizing the electromagnetic waves by frequency and wavelength.

23. Frequency and Waves Higher frequency:
In E-waves: higher freq, higher energy
In Sound waves: higher freq, higher pitch
In sound waves….
Humans can only hear sound waves between 20 Hz and 20,000 Hz
Ultrasonic– above 20,000 Hz
bats, whales, dolphins, cats, dogs,
ultrasound
Infrasonic– below 20 Hz
elephants

24. Doppler Effect
Change in pitch or frequency that occurs when the source of a sound wave is moving relative to an observer.
Lower pitch sound
Higher pitch sound
(higher freq of waves)

25. Doppler Effect
Doppler Shift

26. Speed of sound Terms In air…. 347 m/s In water… 1498 /s
In aluminum… 4877 m/s
Terms
Intensity--- amount of energy that flows through a
certain area at a certain time
Loudness– human perception of sound intensity
Decibels– units to measure sound intensity or loudness
Above 120 dB can cause pain in ears

27. Speed of Waves in different mediums
What happens to the speed of sound as it moves from a solid to liquid to gas?
Why? Slows down cause particles get farther apart and particles take longer to bump into each other and pass on energy.
What happens to the speed of light (ewaves) as it move from a solid to a liquid to a gas?
Why? Speeds up, ewaves don’t need a medium, particles just slow them down. They move fastest through a vacuum…. No medium.

28. Speed of Sound in different temperatures
What happens to the speed of sound as the temperature increases in a material?
Why? As temperature increases, speed of sound increases. Particles move faster and bump into each other more.
True or False?
Sound waves move faster through cold air than hot air. _____
Sound waves move faster through water than air. _________
Radio waves move faster through air than a vacuum._______
Sound waves move faster through a vacuum than air. _______
Gamma rays move faster than light waves through air. ______

29. Go to these websites and TAKE NOTES…
Doppler Effect: Doppler Shift: Seeing Color: (Read and Watch Powerpoint)