Year 9 – Physical ScienceYear 9 – Physical Science

Characteristics of waves

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The Nature of Waves

• A wave is a repeating disturbance or movement that transfers energy through matter or space

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Types of Waves

Some kinds of ENERGY travel in a wave

Do not need a medium to travel through

Needs a medium to travel through

Longitudinal Waves

Transverse Waves

Electromagnetic Waves

Mechanical Waves

Year 9 – Physical ScienceYear 9 – Physical Science

What are the two kinds of mechanical waves?

(a) Transverse Waves

In a transverse wave the matter in the wave moves up and down at a right angle to the

direction of the wave

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Example of a transverse wave:

Light also Light also travels in travels in transverse transverse waveswaves

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(b) Longitudinal Waves (Compression Waves)

In a longitudinal wave the matter in the wave moves back and forth parallel to the

direction of the wave

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Sound waves are an example of compressional waves

•Sound travels as vibrations moving through the air as a compressional wave.

•Sound travels through air, but travels through other materials as well.

•Whales communicate through long distances by producing sounds under water.

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Longitudinal (compressional) wave e.g. soundLongitudinal (compressional) wave e.g. sound

Transverse wave (e.g. light)Transverse wave (e.g. light)

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Year 9 – Physical ScienceYear 9 – Physical ScienceWhat are the parts of a wave?

Transverse wave The crest is the highest point on a transverse wave. The trough is the lowest point on a transverse wave.

The rest position of the wave is called the node or nodal line.

The wavelength is the distance from one point on the wave to the next corresponding adjacent point.

Year 9 – Physical ScienceYear 9 – Physical ScienceThe amplitude of a transverse wave is determined by the height of the crest or depth of the trough

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Parts of a Longitudinal wave

•On a longitudinal wave the area squeezed together is called the compression.

•The areas spread out are called the rarefaction.

•The wavelength is the distance from the center of one compression to the center of the next compression.

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Year 9 – Physical ScienceYear 9 – Physical ScienceSketching WavesSketching Waves

What is the (a) amplitude of this wave, (b) wavelength of What is the (a) amplitude of this wave, (b) wavelength of this wave, (c) frequency of this wave?this wave, (c) frequency of this wave?

WavelengthWavelengthAmplitudeAmplitude