# WAVES Chapter 7.

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WAVES Chapter 7

What is a wave A wave is A rhythmic disturbance
Carries ENERGY but not MATTER

How can a wave carry energy without carrying matter?
Even though the ball is moving from one end of the line to the other, the people are not moving with it.

How do waves move Mechanical Waves Move through matter
Energy moves from particle to particle Examples: Water waves Sound waves Earthquake waves

How do waves move Electromagnetic Waves Move through empty space
Do not require matter or particles in order to move Example: Light waves

Compressional (or Longitudinal) Waves
Types Of Waves Compressional (or Longitudinal) Waves Transverse waves

Parts Of A Wave CREST AMPLITUDE WAVELENGTH TROUGH
high point of a transverse wave AMPLITUDE half the distance between the crest and trough WAVELENGTH TROUGH distance from top of one crest to the top of the next OR from one trough to the next low point of a transverse wave

Properties of waves Amplitude – tells how much ENERGY the wave is carrying Bright light has higher amplitude than dim Loud sounds have higher amplitude than soft Large water waves carry more energy than small ones

Properties of waves Red has a longer & Violet has a shorter
Wavelength (λ)– In visible light, λ determines color λ λ Red has a longer & Violet has a shorter λ Radio waves and microwaves have longer λ X-rays and gamma ray have shorter

Properties of waves Frequency – the number of λ that pass a given point in one second, measured in λ/sec = hertz Higher frequency indicates faster vibration of whatever is generating the wave

Frequency and wavelength are closely related Short λ creates a higher frequency In sound, this causes a higher pitch In light, violet color has a higher frequency than red Long λ creates a lower frequency In sound, this causes a lower pitch In light, red color has a lower frequency than violet CLICK HERE > F = < λ

Properties of waves WAVE SPEED Mechanical Wave
Travels faster through solids because molecules are closer together and transmit the sound better Electromagnetic Wave Travels faster through empty space because there are no molecules in the way to slow it down

When sound waves reflect from a surface, it produces an ECHO.
Wave Behavior Reflection: a wave strikes a surface and bounces off HELLOOOO!!! HELLOOOO!!! Reflection are clear when they bounce off a smooth, even surface. From a rough surface, light scatters in all directions and the reflection is distorted. When sound waves reflect from a surface, it produces an ECHO.

Wave Behavior Refraction: The bending of a wave as it moves from one medium into another because of a change in SPEED.

Diffraction occurs better when the barrier and λ are similar in size.
Wave Behavior Diffraction: The bending of waves around a barrier. LIGHT WAVES Light waves do not diffract as much as sound waves, so you can’t see around corners. This is because the λ of light is so much smaller than the width of a door. Diffraction occurs better when the barrier and λ are similar in size. SOUND WAVES You can hear sounds from a room even when you are not in the room because the sound waves bend as they pass through the open doorway WATER WAVES When water waves strike obstacles such as islands, they bend around the island and keep moving. If the island was much bigger than than the wavelength of the water wave, less diffraction would occur

Wave Behavior Interference: The ability of two waves to combine and form a new wave when they overlap

INTERFERENCE CONSTRUCTIVE Interference

INTERFERENCE CONSTRUCTIVE Interference

INTERFERENCE CONSTRUCTIVE Interference

INTERFERENCE DESTRUCTIVE Interference

INTERFERENCE DESTRUCTIVE Interference

INTERFERENCE DESTRUCTIVE Interference

Constructive INTERFERENCE
The crests of two waves – A & B – approach each other The two waves form a wave with a greater amplitude while the crests of both waves overlap

Constructive INTERFERENCE
The original waves pass through each other and go on as they started.

Destructive INTERFERENCE
The crest of one wave (A) approaches the trough of another (B) If the two waves have equal amplitude, they momentarily cancel when they meet

Destructive INTERFERENCE
The original waves pass through each other and go on as they started.

Parts of a COMPRESSIONAL WAVE:
Parts Of A Wave Parts of a COMPRESSIONAL WAVE: Compression Rarefaction Wavelength

What did you learn