Waves and EnergyWaves and Energy

Physics, Grade 8Physics, Grade 8

Types of WavesTypes of Waves

Mechanical WavesMechanical Waves need matter need matter (medium) to travel through(medium) to travel through

Electromagnetic WavesElectromagnetic Waves can travel can travel through empty spacethrough empty space

Mechanical WavesMechanical Waves May be longitudinal May be longitudinal

(compression)(compression)

Or transverseOr transverse

Transverse WavesTransverse Waves

Transverse waves move like a Transverse waves move like a snake going up and downsnake going up and down

Light energy moves in Light energy moves in transverse wavestransverse waves

Parts of a transverse wave:Parts of a transverse wave:

As wavelength increases, frequency As wavelength increases, frequency decreasesdecreases

AmplitudeWavelength

Trough

Crest

How often = Frequency

Compression WavesCompression Waves

Compression waves move like a Compression waves move like a worm, squeezing and releasingworm, squeezing and releasing

Sound energy moves in compression Sound energy moves in compression waveswaves

Longitudinal/Compression WavesLongitudinal/Compression Waves – – energy energy must must move along the move along the medium while traveling forwardmedium while traveling forward

Transverse Both Longitudinal

Moves in compressions (pulses) in same direction the wave does

Example: sound waves

Both have a frequencywavelength, amplitude

Both transfer energy from one place to another

Wave moves up and down or side to side while traveling forward

Example: light waves

Review :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?

ElectromagnetiElectromagnetic Waves c Waves

ObjectivesObjectives

-Define electromagnetic radiation.-Define electromagnetic radiation. -Identify positive and negative -Identify positive and negative

effects of waves on human activitieseffects of waves on human activities -Compare and contrast the differing -Compare and contrast the differing

frequencies and energy levels of frequencies and energy levels of waves in the electromagnetic waves in the electromagnetic spectrumspectrum

Focus QuestionFocus Question

What effect does increasing frequency and wavelength have on energy of waves?

Electromagnetic (EM) wavesElectromagnetic (EM) waves Light is an electromagnetic wave.Light is an electromagnetic wave.

EM waves are made up of 2 fields: EM waves are made up of 2 fields: electric and magnetic.electric and magnetic.

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

Types of em wavesTypes of em waves

Radio WavesRadio Waves

Longest wavelengths and lowest Longest wavelengths and lowest frequencies.frequencies.

Lowest energy.Lowest energy. Used to carry sound and picture info to Used to carry sound and picture info to

TVs and radios.TVs and radios.

MicrowavesMicrowaves More energy than radio waves.More energy than radio waves. Used in microwave OVENS and radar Used in microwave OVENS and radar

guns.guns.

Draw a picture of something that will Draw a picture of something that will help you remember microwaves. help you remember microwaves.

Note: MicrowavesNote: 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.

Infrared WavesInfrared Waves

More energy than radio waves and More energy than radio waves and microwaves.microwaves.

Infrared waves from the sun make you Infrared waves from the sun make you feel warm.feel warm.

Draw a picture of something that will help Draw a picture of something that will help you remember infrared waves. you remember infrared waves.

Visible LightVisible Light

The kind of light that humans can The kind of light that humans can see.see.

Includes the colors ROY G BIV.Includes the colors ROY G BIV. Red has long waves; violet has short Red has long waves; violet has short

waveswaves Draw a picture Draw a picture of something that will of something that will

remind you of visible light.remind you of visible light.

Ultraviolet (UV) LightUltraviolet (UV) Light

More energy than visible lightMore energy than visible light Used to kill bacteria on food or surgical Used to kill bacteria on food or surgical

instruments.instruments. UV rays from the sun can cause sunburn UV rays from the sun can cause sunburn

or cancer.or cancer. Absorbed by the ozone layer.Absorbed by the ozone layer.

Draw a picture Draw a picture of something that will of something that will remind you of Ultraviolet Light.remind you of Ultraviolet Light.

X-RaysX-Rays

Can be used to take pictures of the Can be used to take pictures of the inside of your body.inside of your body.

Have large amounts of energy.Have large amounts of energy.

Draw a pictureDraw a picture of something that will of something that will remind you of X-Raysremind you of X-Rays

Gamma RaysGamma Rays Carry the most energy of all wavesCarry the most energy of all waves Highest frequency & shortest wavelengthHighest frequency & shortest wavelength Used to kill cancer cellsUsed to kill cancer cells Given off in nuclear reactionsGiven off in nuclear reactions Most dangerous to humans!Most dangerous to humans!

Draw a picture Draw a picture of something that will remind of something that will remind you of gamma rays.you of gamma rays.

Look at your spectrum.Look at your spectrum. What happens to the wavelength of EM What happens to the wavelength of EM

waves as you move right along the waves as you move right along the spectrum?spectrum? The wavelength gets SHORTER as you move The wavelength gets SHORTER as you move

up the spectrum.up the spectrum.

What happens to the frequency of EM What happens to the frequency of EM waves as you move up the spectrum to waves as you move up the spectrum to the right?the right? The frequency gets HIGHER as you move up The frequency gets HIGHER as you move up

the spectrum.the spectrum.

Which waves have the least energy?Which waves have the least energy? Waves on the left have less energy. Waves on the left have less energy.

Radio wavesRadio waves have the least. have the least.

Which waves have the most energy?Which waves have the most energy? Waves on the right have more energy. Waves on the right have more energy.

Gamma rays Gamma rays have the most.have the most.

Which waves have a longer Which waves have a longer wavelength?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?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?

Which waves have more energy?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?

Answer this on the back of your Answer this on the back of your EMS:EMS:

There are many types of EM waves. There are many types of EM waves. Which types do you think are the Which types do you think are the best or the most useful? Pick 1 or 2, best or the most useful? Pick 1 or 2, and explain to me why you chose and explain to me why you chose them. Write at least 4 sentences.them. Write at least 4 sentences.

This will be graded!This will be graded!