Mr. Jackson 4-15-11 Ch 20

What is a Wave? A disturbance that transmits energy through matter or empty space Energy can be carried away from its source by a wave. If you drop a rock on a lake the rock will form a wave but the wave will not move any object on top of the water. See Ex

Medium A medium is a substance through which a wave travels. The plural of medium is media Sound waves require a medium whereas light waves do not.

Waves that Need a Medium are called mechanical waves Waves that Need a Medium are called mechanical waves. Earthquakes are a good example of a mechanical wave

Energy Transfer Without a Medium Visible light, microwaves, TV and Radio Waves as well as X-Rays are waves that do not require a medium

Transverse Waves This is what you would think of when you think of a wave A wave in which the particles of the medium move perpendicularly to the direction of wave travel

Longitudinal waves Looks like a slinky or spring When the particles of the medium move in the direction of the wave. When the spring’s rings are close together the part of the wave is called a compression When they are pulled apart they are called rarefactions

Amplitude Amplitude is the Maximum distance a wave travels from its rest position

Wavelength The distance from any point on a wave to an identical point on another wave

The shorter the wavelength the more energy a wave has

Frequency Expressed in Hertz Hz 1 wave in 1 sec = 1 Hz 103.7, 106.9 ect

FM FM Radio represents Frequency Modulation When The Frequency of a wave is modulated the Wave’s Frequency is refocused as it is transmitted

AM AM is Amplitude Modulation This is where the wave’s Amplitude is refocused when broadcasted

Wave Speed Wave speed is calculated by Multipling Wavelength x Frequency

More on Wave properties As a wave’s Frequency is doubled the wavelength is cut in half If wavelength is doubled the Frequency is cut in half

Reflection Reflection is the bouncing back of a wave when it hits a barrier All waves can be reflected If a wave passes through a substance is it said to be transmitted

Refraction The Bending of a wave When a wave passes from one medium to another it changes its speed and wavelength therefore it bends

Diffraction The change of direction by a wave when it encounters a barrier. Ex Sound coming from around a corner

Interference When 2 or more waves overlap and form 1 wave

Constructive interference When the crest of 1 wave overlaps the crest of another wave. The result is a wave with higher amplitude

Destructive interference When the crest of one wave overlaps with the trough of another wave This reduces the amplitude

Standing waves In a standing wave one part of the wave is always at rest due to total destructive interference. Other parts of the wave have a high Amplitude A standing wave appears to be standing still Playing a guitar produces standing waves

Resonance When an object close to the source object vibrating begins to vibrate All musical instruments resonate to produce loud full sounds