1. Waves and Energy
Physics, Grade 8

2. Types of Waves Mechanical Waves need matter (medium) to travel through
Electromagnetic Waves can travel through empty space

3. Mechanical Waves
May be longitudinal (compression)
Or transverse

4. Transverse Waves Transverse waves move like a snake going up and down
Light energy moves in transverse waves

5. Parts of a transverse wave:
As wavelength increases, frequency decreases
Wavelength
Amplitude
Crest
Trough
How often = Frequency

6. Compression Waves
Compression waves move like a worm, squeezing and releasing
Sound energy moves in compression waves

7. Longitudinal/Compression Waves – energy must move along the medium while traveling forward

8. Transverse Both Longitudinal
Moves in compressions (pulses) in same direction the wave does
Example: sound waves
Both have a frequency
wavelength, amplitude
Both transfer energy from one place to another
Wave moves up and down or side to side while traveling forward
Example: light waves

9. Review : Which letter shows the amplitude of the wave at right?
Which letter shows a wavelength of the wave at right?
When frequency increases, what happens to the wavelength? b c d a

10. Electromagnetic Waves

11. Objectives -Define electromagnetic radiation.
-Identify positive and negative effects of waves on human activities
-Compare and contrast the differing frequencies and energy levels of waves in the electromagnetic spectrum

12. Focus Question
What effect does increasing frequency and wavelength have on energy of waves?

13. Electromagnetic (EM) waves
Light is an electromagnetic wave.
EM waves are made up of 2 fields: electric and magnetic.

14. All EM waves travel at the same speed  the speed of light (c). c = λ f

15. Types of em waves

16. Radio Waves Longest wavelengths and lowest frequencies. Lowest energy.
Used to carry sound and picture info to TVs and radios.

17. Microwaves More energy than radio waves.
Used in microwave OVENS and radar guns.
Draw a picture of something that will help you remember microwaves.

18. This is a microwave OVEN
Note: Microwaves
This is a microwave OVEN
This is a MICROWAVE
Microwaves are used IN microwave ovens to help cook the food.
Microwaves are EM waves. Microwave OVENS are NOT EM waves.

19. Infrared Waves More energy than radio waves and microwaves.
Infrared waves from the sun make you feel warm.
Draw a picture of something that will help you remember infrared waves.

20. Visible Light The kind of light that humans can see.
Includes the colors ROY G BIV.
Red has long waves; violet has short waves
Draw a picture of something that will remind you of visible light.

21. Ultraviolet (UV) Light
More energy than visible light
Used to kill bacteria on food or surgical instruments.
UV rays from the sun can cause sunburn or cancer.
Absorbed by the ozone layer.
Draw a picture of something that will remind you of Ultraviolet Light.

22. X-Rays Can be used to take pictures of the inside of your body.
Have large amounts of energy.
Draw a picture of something that will remind you of X-Rays

23. Gamma Rays Carry the most energy of all waves
Highest frequency & shortest wavelength
Used to kill cancer cells
Given off in nuclear reactions
Most dangerous to humans!
Draw a picture of something that will remind you of gamma rays.

24. Look at your spectrum.
What happens to the wavelength of EM waves as you move right along the spectrum?
The wavelength gets SHORTER as you move up the spectrum.
What happens to the frequency of EM waves as you move up the spectrum to the right?
The frequency gets HIGHER as you move up the spectrum.

25. Which waves have the least energy?
Waves on the left have less energy. Radio waves have the least.
Which waves have the most energy?
Waves on the right have more energy. Gamma rays have the most.

26. Which waves have a longer wavelength?
Radio or Gamma?
Ultraviolet or Infrared?
Microwaves or Visible Light?
Which waves have a higher frequency?
Visible Light or X-Rays?
Microwaves or Infrared?
Ultraviolet or Visible Light?

27. Which waves have more energy?
Radio or Gamma?
Ultraviolet or Infrared?
Microwaves or Visible Light?

28. Answer this on the back of your EMS:
There are many types of EM waves. Which types do you think are the best or the most useful? Pick 1 or 2, and explain to me why you chose them. Write at least 4 sentences.
This will be graded!