1. WAVES

2. The Energy of Waves
Wave - any disturbance that transfers energy through matter or empty space
Waves transmit energy
As a wave travels, it does work on everything in its path.
Many waves transfer energy by the vibration of particles in a medium.

3. The Energy of Waves
Medium (media) – a material that is disturbed by a wave; a substance through which a wave can travel (solid, liquid, or gas)
When particles vibrate, they are passing energy to the particle next to them.
If there are not any particles to vibrate, sound isn’t possible.
Waves that need a medium (sound, ocean, seismic) are called mechanical waves.

4. The Energy of Waves
Some waves can transfer energy WITHOUT going through a medium: visible light, microwaves, TV and radio signals, and X rays
Waves that DO NOT need a medium are called electromagnetic waves.
Even though electromagnetic waves do not need a medium, they can still go through matter (air, water, glass).

5. Mechanical Waves – require a medium
Sound waves (air)
Ocean waves (water)
Seismic waves (earth)
Electromagnetic Waves – do NOT require a medium
Light waves
Microwaves
Radio waves/television waves
X-rays

6. Types of Waves Transverse Wave Particles move in an up and down motion
The particles of the medium vibrate perpendicular (right angle) to the path of the wave
Seismic waves, light waves, and electromagnetic waves are transverse waves
They have a crest and a trough

7. Types of Waves

8. Particles of the medium vibrate parallel to the path of the wave
Longitudinal Wave
Like a spiral or slinky
Particles of the medium vibrate back and forth along the path that the wave moves
Particles of the medium vibrate parallel to the path of the wave
Sound waves are longitudinal waves

9. Longitudinal Wave Compression – particles pushed closer together
Rarefaction – particles spread out

10. Surface Waves Form at or near the boundary between two media
A combination of a transverse and a longitudinal wave
Particles of the medium move in circles
Particles move forward at the crest and backward at the trough
Ocean waves are surface waves

11. Properties of Waves
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12. amplitude
crest
wavelength
trough
frequency

13. (add these definitions to your foldables)
Crest- the highest point of a transverse wave.
Illustrate on the back of the flap
Trough- the lowest point between two crests.
Amplitude – the distance from the midpoint (resting position) to its crest or trough
Large amplitude = more energy
Small amplitude = less energy

14. Wavelength – the distance from any point on a wave to the identical point on the next wave
Shorter wavelength = more energy
Longer wavelength = less energy
Frequency – the number of waves that pass a given point in one second; measured in hertz (Hz)
(1Hz = 1 wave per second)
High frequency = more energy
Low frequency = less energy

15. Energy of Waves Chart
Wave Description Wave Energy Drawing Larger amplitude more energy Small amplitude less energy Shorter wavelength more energy Longer wavelength less energy High frequency more energy Low frequency less energy

16. Wave Interactions
Reflection - when a wave bounces back after hitting a barrier
Light waves from the sun reflecting off the moon
Echo – sound waves reflecting off a barrier
Transmitted Waves – when a wave passes through a barrier
A glass window allows light waves to pass through.

17. Refraction – the bending of a wave as the wave passes from one medium to another
Wave speed changes
Which causes wavelength to change
Travels in a new direction
Example
the pencil looks broken in a glass of water because the light wave is passing from air into water and
the speed of the wave changed

18. Diffraction - the bending of waves around a barrier or through an opening.
Waves usually travel in a straight line
But they may curve or bend when the wave reaches the edge of an object
Depends on the wavelength and size of barrier or opening
Example: You can hear music around the corner of a building, but cannot see who is playing the music
Sound waves have longer wavelengths & diffract better
Light waves have shorter wavelengths

19. Interference - the combination of two or more waves to form a single wave.
Constructive interference – when the crests and troughs of one wave overlap with the crests and troughs of another wave
Energy of each wave adds together to make a higher energy wave
Higher crests
Deeper troughs
Higher amplitude
Add picture of constructive interference

20. Destructive interference – when the crests of one wave overlap with the troughs of another wave
The energy of the new wave is less than the energy of both waves and has a lower amplitude
If a crest and trough of the same amplitude meet, the result is no wave at all
Add picture of destructive interference
HMub3Jn/book/McKinney-7th-Grade-Integrated- Science-Flexbook/r125/section/106.0/

21. Electromagnetic Wave