Waves 2014

Waves NotesWaves Notes

Wave Wave TypesTypes

Transverse wave  • The motion of the medium is at right angles

to the direction the wave is moving. Particles of the medium move up and down, but not horizontally.

Wave TypesWave TypesLongitudinal wave • The motion of the medium is parallel to the

direction the wave is moving. Particles of the medium move horizontally, but not up and down.

Amplitude - (wave height)• The maximum distance molecules are

displaced from their rest position. • Amplitude indicates the energy of the

wave.

Wave Wave CharacteristicCharacteristics:s:

Wavelength - • The distance between two consecutive crests of a

wave. • Symbol for wavelength is the Greek letter lambda -

Wave Characteristics:Wave Characteristics:

Frequency - • The number of complete waves per unit

of time. • Hertz (Hz) - The units of wave frequency. • 1 Hz = 1 wave / sec

Wave Wave CharacteristicCharacteristics:s:

Wave speed - • Wave speed depends on the medium in

which it travels. • In a given medium, the speed of a wave

is constant. Wave speed is calculated by the equation:

Speed = (frequency) (wavelength)

Wave Characteristics:Wave Characteristics:

Wavelengths Wavelengths GraphGraph

SounSound:d:

• Longitudinal waves composed of a series of compressions and rarefactions.

• Mechanical – they must travel through a medium.

• Sound waves cannot travel in the Sound waves cannot travel in the vacuum of spacevacuum of space because there is because there is no medium to transmit these no medium to transmit these mechanical waves.mechanical waves.

• Longitudinal waves composed of a series of compressions and rarefactions.

• Mechanical – they must travel through a medium.

• Sound waves cannot travel in the Sound waves cannot travel in the vacuum of spacevacuum of space because there is because there is no medium to transmit these no medium to transmit these mechanical waves.mechanical waves.

Intensity - • The amount of energy in a wave. • Intensity determines the amplitude of a

wave. • Intensity relates to the loudness of a sound

- the greater the intensity, the louder the sound.

• Decibels - the units of intensity. • Sounds over 120 decibels will cause pain

in the ears. • Ear damage can begin with exposure to

sounds as low as 85 decibels.

Properties of Sound

Pitch - • How low or high the sound is. • The frequency of a wave determines its

pitch. • Pitch is related to frequency - the higher

the frequency, the higher the pitch. • The human ear can hear sounds ranging

from 20 Hz to 20,000 Hz. • Sounds over 20,000 Hz are called

ultrasonic. • Thunder has a low pitch with a frequency

less than 50 Hz. • A whistle has a high pitch with a frequency

close to 1000 Hz.

Properties of Sound

Light:Light:

• Visible lightVisible light is the is the

portion of the electromagnetic portion of the electromagnetic spectrum that we can see.spectrum that we can see.

• As the full spectrum of visible light As the full spectrum of visible light travels through a prism, the travels through a prism, the wavelengthswavelengths separate into the separate into the colors of the rainbow because each colors of the rainbow because each colorcolor is a different wavelength. is a different wavelength.

• As objects grow As objects grow hotterhotter, they , they radiate energy dominated by radiate energy dominated by shortershorter wavelengths. wavelengths.

• The color of stars tells scientists The color of stars tells scientists about their about their

temperaturetemperature..

Light: Light: COLOR AND COLOR AND TEMPERATURETEMPERATURE

Light: Light: COLOR AND COLOR AND TEMPERATURETEMPERATURE

• Our Sun produces more Our Sun produces more yellow lightyellow light than any other color because its than any other color because its surface temperature is surface temperature is 5,500°C5,500°C. .

• The star Betelgeuse is The star Betelgeuse is coolercooler——about 3,000°C—and looks about 3,000°C—and looks reddishreddish. .

• The star Rigel is The star Rigel is hotterhotter—about —about 12,000°C—and looks 12,000°C—and looks blueblue..

Radio Radio WavesWaves•Radio waves have the Radio waves have the longestlongest

wavelengths in the wavelengths in the electromagnetic (EM) electromagnetic (EM) spectrum.spectrum.

•They range from the length of They range from the length of a a footballfootball to larger than our to larger than our planetplanet..

Radio Waves:Radio Waves:Radio Emissions in the Radio Emissions in the Solar SystemSolar System

•Astronomical objects that have Astronomical objects that have a a changing magnetic fieldchanging magnetic field can can produce radio waves.produce radio waves.

•Radio telescopesRadio telescopes look toward look toward the heavens to view planets, the heavens to view planets, comets, giant clouds of gas comets, giant clouds of gas and dust, stars, and galaxies. and dust, stars, and galaxies.

Radio Waves:Radio Waves:Radio Emissions in the Radio Emissions in the Solar SystemSolar System

• By studying the radio waves By studying the radio waves originating from these sources, originating from these sources, astronomers can learn about their astronomers can learn about their compositioncomposition, , structurestructure, and , and motionmotion..