Waves

What are waves?

a disturbance that transfers energy from place to place.

Classified as either

1. Mechanical- require a medium2. Electromagnetic- do not require a

mediumLight, radio, x-rays, and gamma raysare some examples of e/m waves.

Define mediumThe material through which a wave

travels

Ex. Gases (air), liquids (water) and solids (rope)

Mechanical WavesClassified as either

Longitudinal: A wave that moves a medium in a direction parallel to thedirection in which the wave travels.

Transverse: A wave that moves the medium in a direction

perpendicular to the direction in which the wave travels.

Types of Mechanical Waves

Longitudinal• The part of a longitudinal wave

where the particles of the medium are far apart are called

rarefactions.• The part of a longitudinal wave

where the particles of the medium are close together are called

compressions.

Surface Waves

TRANSVERSE WAVES

• Transverse Waves are waves in which the particles vibrate perpendicularly to the direction the wave is traveling.

• Transverse waves are made up of crests and troughs.

• Water waves, waves on a rope, and electromagnetic waves are examples of transverse waves.

http://www.acs.psu.edu/drussell/Demos/waves/wavemotion.html

Crests and Troughs of Transverse Waves

• Transverse waves have alternating high points and low points.

• The high point of a wave is a crest.• The low point of a wave is a trough.

AmplitudeWavelengthFrequency

Speed

Amplitude

• The amplitude of a wave is the maximum distance that the particles of a medium vibrate from their rest position.

A wave with a large amplitude carries more energy than a wave with a small amplitude does.

WAVE SPEED

is Speed - the speed of a wave is how far the wave travels in a given length of time.the speed at which a wave travels. • The speed depends on the medium a wave travels

through.• Waves usually travel faster in liquids and solids than

they do in gases.Speed = wavelength x frequency

s = l x f

Wave FrequencyFrequency - the number of complete waves that pass a given point in a certain

amount of time.• Frequency can be found by counting the number of crests

or troughs that pass a point each second.• Frequency is usually expressed in hertz (Hz). One hertz

equals one wave per second.• High frequency means more waves per second.• Low frequency means fewer waves per second.

WAVELENGTH

• A wavelength is the distance between any point on a wave to an identical point on the next wave.

Energy in WavesDecreased Energy long wavelengthsmall amplitudelow frequency

Increased Energy short wavelength large amplitude high frequency

Wave Demonstrationshttp://www.acs.psu.edu/drussell/Demos/waves/w

avemotion.html