waves. examples –water waves –sound waves –light waves –radio waves –microwaves

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Waves

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• Examples– Water waves– Sound waves– Light waves– Radio waves– microwaves

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Waves are everywhere

• Part of everyday life

• Waves carry oscillations from one place to another – earthquakes

• Waves carry information and energy

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Types of waves

• Transverse

– Oscillations perpendicular to direction the wave moves

– Oscillates up and down

– Wave moves left to right

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• Longitudinal wave

– Oscillations in same direction of wave movement

– Compressions

– rarefactions

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Basic Properties

• Frequency- how often wave goes up and down– Measured in hertz

• Amplitude- max distance above the level surface

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• Wavelength- length of one complete cycle of a wave– Crest to crest or trough to trough– lambda

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• Speed- how fast the wave transmits an oscillation– Water- few mph– Light- 186,000 mph– Sound- 660 mph

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• Speed of wave is NOT up-down speed of surface

• To measure speed, start ripple and measure how long it takes to affect a distant place

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• Speed of wave =

wavelength x frequency

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Wave shapes

• Crests

• Troughs

• Plane waves

• Circular waves

Plane wave

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Circular wave

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Wave interactions

• Reflection- bounce off and go in new direction

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• Refraction- wave passes into and through obstacle

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• Diffraction- Wave bends around or through holes in obstacle

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• Absorption- wave absorbed and disappears

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Sound

Ear

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How do we hear?

1. Eardrum vibrates as sound waves enter ear canal

2. 3 bones of inner ear -hammer (malleus), anvil (incus), stirrup (stapes) transmit vibrations to cochlea

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• 3. Cochlea- fluid filled organ responsible for hearing as well as balance- fluid vibrates and creates waves that travel up spiral and stimulate tiny hairs (receptor cells)

– Nerves near large end respond to longer wavelengths, lower frequencies

– Nerves near narrow end respond to shorter wavelengths, higher frequencies

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Human Hearing

• Range of human hearing (20-20,000 Hz)

• Hearing ability changes with people and age

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• Hearing can be damaged by loud noise

• Tiny hairs in cochlea will weaken or break

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Ultrasound

• Greater than 100,000 Hz- passes through human body easily

• Refractions and reflections inside body used to create images.

Properties of Sound

• Air - molecules in constant random motion– Air pressure

• Anything that vibrates produces sound waves as long as there is air or other material

Longitudinal wave

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Loudness of Sound• Decibel scale (dB)- related to amplitude

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• For every increase of 20 dB = 10 times greater amplitude

• Ears are very sensitive- detect differences in sound waves that are 2 parts out of 100 million!= EASILY DAMAGED