WAVES CARRY ENERGY!WAVES CARRY ENERGY!

Waves are rhythmic disturbances that carry ENERGY without carrying matter. Molecules transport the energy in a wave by colliding with the molecules around them. Mechanical waves travel through matter by creating vibrations in a medium – solid, liquid or gas. Examples: Sound, water or seismic waves.

MECHANICAL WAVESMECHANICAL WAVES

Use matter to transfer ENERGY from particle to particle Use matter to transfer ENERGY from particle to particle

Matter = MediumMatter = Medium(requires it) (requires it)

TRANSVERSETRANSVERSE COMPRESSIONALCOMPRESSIONAL(Longitudinal)(Longitudinal)

CREST

TROUGH

WAVELENGTH

WAVE PROPERTIESWAVE PROPERTIES

CREST – highest point of a waveTROUGH – lowest point of a waveWAVELENGTH – distance from peak to peakAMPLITUDE – the distance a wave rises/falls from its rest positionFREQUENCY – the number of waves passing a given point

AMPLITUDE

REST POSITION

FREQUENCY

Frequency and Wavelength

Longer wavelengths Larger frequencies result in smaller result in shorterfrequencies. wavelengths.

As the frequency of a wave increases, its wavelength decreases.

Frequency and wavelength are related!

• oscillating, repetitive motion in which the medium moves at right angles to the wave direction• particles of the medium moving perpendicular (moves at right angle)

TRANSVERSE WAVESTRANSVERSE WAVES

EXAMPLES: EXAMPLES: Slinky, secondary seismic wave, ocean waves, light waves, guitar strings, and a stadium wave

WAVELENGTHWAVELENGTH

TROUGHTROUGH

AMPLITUDEAMPLITUDE

CRESTCREST

COMPRESSIONAL WAVESCOMPRESSIONAL WAVES• particles of the medium moving parallel to the direction of the wave • oscillating, repetitive motion that moves in the same direction as the medium• matter in the medium moves forward or backward in the same direction of the wave• Transfers energy from molecule to molecule through solids, liquids & gases• Needs a medium to travel – space is a vacuum without air – sound does not travel in space

EXAMPLESEXAMPLES - Sound, dominoes, primary seismic waves, bats hearing, sonar

WAVELENGTH COMPRESSION

RAREFACTION]] ]

Field - force or push in a regionSpeed of light – 300,000 kmpsMedium - matter Electromagnetic waves travel in a vacuum at the same speed

Electromagnetic waves are not caused by a disturbance of particles in a medium. Instead, it is produced by an interaction between an electric and a magnetic field.

ELECTROMAGNETIC ELECTROMAGNETIC SPECTRUMSPECTRUM

Gamma Rays

Cosmic rays

Radio waves

HIGH

Visible Light

Frequency LOW

100,

000,

000

1 100

10,0

00

1,00

0,00

0

0.01

0.00

0,1

0.00

0,00

1

0.00

0,00

0,01

0.00

0,00

0,00

0,1

0.00

0,00

0,00

0,00

1

0.00

0,00

0,00

0,00

0,00

0,1

0.00

0,00

0,00

0,00

0,01

WavelengthShort Long

Ultraviolet InfraredInfrared

X-rays Microwave

(192)

ELECTROMAGNETIC WAVESELECTROMAGNETIC WAVES• Are transverse waves that do not require matter to carry energy. • They are produced by the motion of electrically charged particles.

• They can travel through solid, liquids or gas faster than mechanical waves.

• They can also travel through space, or through a vacuum where no matter exist.

• Light is a electromagnetic wave that travels through air at about 300,000 km/s.

• Bright lights have greater amplitudes (more energy) than the waves that make up dim light.

• Because frequency and wavelength are related, either the wavelength or frequency of a light wave determines the color of the light. Blue light has a larger frequency and shorter wavelength than red light. Red light has a shorter frequency and a longer wavelength.

• Light travels faster through gases than in solids or liquids. Example: speed of light is one and a half times faster in air than

it is in glass.

LIGHT WAVE BEHAVIOR

• Reflected

• Absorbed

• Transmitted

Light rays that come in contact with a object that reflects it willbounce right back at the same angle it came in at - like your reflection In a mirror.

Light rays that come in contact with a dark object will be absorbed into it, making the object warmer - like your darkcolored shirt or car.

Light rays that come in contact with something that is translucent, or clear, will “transmit” or go through the object - like a window or a glass.

A MIRAGE IS AN ILLUSION CAUSED BY THE REFRACTION OF LIGHT WAVES, MAKING OBJECTS THAT ARE FAR AWAY TO BE NEARBY, FLOATING IN THE AIR OR UPSIDE DOWN.

Light rays refract as they enter and leave each Light rays refract as they enter and leave each rain drop. Each color refracts at different angles rain drop. Each color refracts at different angles because of their different wavelengths, so they because of their different wavelengths, so they separate into the colors of the spectrum.separate into the colors of the spectrum.

As sunlight passes through the atmosphere, its wavelength is scattered by particles of dust in the air. Red and yellow wavelengths pass through the air directly, while blue light is scattered. It is this scattered blue light (short wavelength) that reaches our eyes when we see blue sky.

SOUND• Sound is a mechanical wave that travels through air at about

340 m/s or 1100 ft. per second.• Loud sound waves are greater amplitudes than soft sound

waves.• Loud sounds carry more energy than soft sounds.• Sound travels faster in a solid than a liquid, and faster in a

liquid than a gas.• In a sound wave, either the wavelength or frequency determines

the pitch.• Pitch is the high or low of a sound.• Sound level (loudness) is measured in units called decibels.• Vocal cords produce sound by vibration. • As the frequency of a sound wave increases, its wavelength

decreases.