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Waves and Energy Physics, Grade 8. Types of Waves Mechanical Waves need matter (medium) to travel through Mechanical Waves need matter (medium) to travel.

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Presentation on theme: "Waves and Energy Physics, Grade 8. Types of Waves Mechanical Waves need matter (medium) to travel through Mechanical Waves need matter (medium) to travel."— Presentation transcript:

1 Waves and Energy Physics, Grade 8

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

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

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

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

6 Compression Waves Compression waves move like a worm, squeezing and releasing Compression waves move like a worm, squeezing and releasing Sound energy moves in compression waves 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 : b c d a 1.Which letter shows the amplitude of the wave at right? 2.Which letter shows a wavelength of the wave at right? 3.When frequency increases, what happens to the wavelength?

10 Electromagnetic Waves

11 Objectives -Define electromagnetic radiation. -Define electromagnetic radiation. -Identify positive and negative effects of waves on human activities -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 -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. Light is an electromagnetic wave. EM waves are made up of 2 fields: electric and magnetic. 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 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. Longest wavelengths and lowest frequencies. Lowest energy. Lowest energy. Used to carry sound and picture info to TVs and radios. Used to carry sound and picture info to TVs and radios.

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

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

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

21 Ultraviolet (UV) Light More energy than visible light More energy than visible light Used to kill bacteria on food or surgical instruments. Used to kill bacteria on food or surgical instruments. UV rays from the sun can cause sunburn or cancer. UV rays from the sun can cause sunburn or cancer. Absorbed by the ozone layer. Absorbed by the ozone layer. Draw a picture of something that will remind you of Ultraviolet Light. 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. Can be used to take pictures of the inside of your body. Have large amounts of energy. Have large amounts of energy. Draw a picture of something that will remind you of X-Rays Draw a picture of something that will remind you of X-Rays

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

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

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

27 Which waves have more energy? Radio or Gamma? Radio or Gamma? Ultraviolet or Infrared? Ultraviolet or Infrared? Microwaves or Visible Light? 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. 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! This will be graded!


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