Waves. Examples –Water waves –Sound waves –Light waves –Radio waves –microwaves

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Waves



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



Waves are everywhere

• Part of everyday life

• Waves carry oscillations from one place to another – earthquakes

• Waves carry information and energy



Types of waves

• Transverse

– Oscillations perpendicular to direction the wave moves

– Oscillates up and down

– Wave moves left to right





• Longitudinal wave

– Oscillations in same direction of wave movement

– Compressions

– rarefactions





Basic Properties

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

• Amplitude- max distance above the level surface



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



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



• 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



• Speed of wave =

wavelength x frequency



Wave shapes

• Crests

• Troughs

• Plane waves

• Circular waves

Plane wave



Circular wave



Wave interactions

• Reflection- bounce off and go in new direction



• Refraction- wave passes into and through obstacle



• Diffraction- Wave bends around or through holes in obstacle



• Absorption- wave absorbed and disappears





Sound

Ear





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



• 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





Human Hearing

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

• Hearing ability changes with people and age



• Hearing can be damaged by loud noise

• Tiny hairs in cochlea will weaken or break



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







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



• 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

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Waves. Examples –Water waves –Sound waves –Light waves –Radio waves –microwaves