# What Are Some Properties of Waves

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What Are Some Properties of Waves
Unit E, Chapter 4, Section 1 pE

Waves Wave: disturbance that travels through matter or space, carrying energy from one place to another without carrying matter with it Information we receive travels in waves Light, sound, radio, televisions, Mechanical waves: waves that need matter to travel through Substance, matter, only vibrates back & forth or side-to-side Floating object Bobs up and down Doesn’t move in direction of waves Waves don’t transport matter, they only transport energy

Waves Surface waves in water = combination of motion of two kinds of waves Back and forth vibration Side-to-side vibration Resulting motion is circular

Waves Crest: highest part of wave Trough: lowest part of wave
Height: vertical distance between crest and trough Amplitude: distance any point on wave is moved from resting position Equal to ½ height Greater energy of wave, greater amplitude Measured from resting position to crest or trough

Waves Wavelength: horizontal distance between one crest and the next
Always the same in a series of waves Can be measured between any two identical points Amplitude and wavelength of waves can vary greatly

Different Kinds of Waves
Transverse wave: particles vibrate at right angles to direction of wave Yarn moved side-to-side Waves traveled forward Examples: Guitar string Light (Electromagnetic waves) Light doesn’t need a medium, matter, to travel through

Different Kinds of Waves
Longitudinal wave: particles vibrate back and forth in the same direction as the wave is moving Compressions: areas where particles are closer together Rarefaction: areas where particles are spread out Examples: Sound waves Most other waves that travel through liquids or gases

Speed, Frequency, and Wavelength
The speed of a wave is always the same in a particular substance, unless there are changes to the substance Speed of sound through air always the same Change temperature – speed changes Speed of waves through water always the same Change depth – speed changes Speed measured by measuring distance a single point, crest or compression, travels in given time

Speed, Frequency, and Wavelength
Frequency: number of vibrations a wave has in a given time Measured by counting number of crests or compressions passing point in certain amount of time Measured in units called hertz 1 hertz = 1 vibration per second 1 crest passes a point in 1 second 2 hertz = 2 crests passing in 1 second

Speed, Frequency, and Wavelength
Relationship: Speed = wavelength x frequency Increase frequency, wavelength decreases Faster you sent waves down spring, shorter distance between waves

Energy From Waves All waves carry energy in the form of: light, sound, heat, or motion Life on Earth depends on waves carrying energy from sun Heats planet Allowing plants to make food

Energy From Waves People use energy carried in waves Solar panels
Change sun’s light energy into heat or electricity Ocean waves Scientists doing experiments to use energy Advantages: Renewable source Won’t cause pollution from combution

Energy From Waves Energy in waves can also destroy Hurricane waves
Huge amounts of energy Cause almost as much damage as winds Tsunami: waves generated by undersea earthquakes “Tidal waves” Carry greatest amount of energy Begins on ocean floor On surface it not very noticeable When it reaches shore, height may be 35 m (115 ft)

Energy From Waves Energy in waves can also destroy Earthquakes
Seismic waves Energy travels through Earth Both transverse and longitudinal Third kind of wave on surface, similar to water Ground ripples up and down Circular motion

Summary Mechanical waves are disturbances in a substance that carry energy without carrying the substance (matter) Other waves, i.e. light, carry energy without needing matter to travel through Transverse waves displace particles at right angles to the motion of the wave Longitudinal waves displace particles in the same direction as the wave Relationship – speed = wavelength x frequency Some energy from waves can be used, but the energy in waves can also cause great damage

Homework Read Unit E, Chapter 4, Section 1, pE108-113