Energy Transfer - Waves

Waves

• A wave is any disturbance that transmits energy through matter or empty space.

• Energy can be carried away from it’s source by a wave. As a wave travels, it does work on everything in it’s path– Ex. Wave in water – does work to make water

move up and down, to make boats move up and down with the water

Mediums• Energy can be transferred with or without a medium • A medium is a substance through which a wave can travel.• Medium can be solid, liquid, or gas• In a medium, when one particle vibrates, it passes energy

to the particle next to it, which causes the second particle to vibrate.

• Waves that require a medium to travel – Mechanical Waves– Sound waves– Ocean waves

Energy transfer without a medium

• Some waves can transfer energy without going through a medium – Called Electromagnetic Waves– Visible light– Microwaves– Radio waves– Xrays– Although they don’t require a medium, they can

travel through matter (air, water, glass, etc)

Types of Waves

• Waves are classified based on the direction in which the particles of the medium vibrate compared with the direction in which the waves move.

• 3 types of waves– Transverse– Longitudinal– Surface

Transverse waves

• Waves in which the particles of the medium move up-and-down

• The particles of the medium move perpendicularly to the direction the wave is traveling

• The word Transverse means “moving across”

Longitudinal Wave

• The particles of the medium vibrate parallel to the direction of wave motion – Ex: Sound wave

Surface Wave

• When waves form at or near the boundary between two media, a transverse wave and a longitudinal wave can combine to form a Surface Wave

• Look like transverse waves, but the particles of the medium move in circles rather than up and down. They move forward at the crest and backward at the trough

Wave Properties

• Amplitude• Wavelength• Frequency• Speed

Amplitude

• The maximum distance that the particles of a wave’s medium vibrate from their rest position (the rest position is the point where the particles of a medium stay when there are no disturbances.

• More energy transferred = Larger amplitude

Wavelength

• The distance between any two crests or compressions next to each other in a wave OR the distance between any two troughs or rarefactions next to each other

• More energy = shorter wavelength

Frequency• The number of waves produces in a given amount of time –

expressed in hertz (Hz)• For waves: 1 Hz = 1 wave per second• If 2 waves have an equal amplitude – high-frequency waves

carry more energy than low-frequency waves.

Wave Speed

• The speed at which a wave travels• Speed (v) Can be calculated using wavelength

(λ – greek lambda) and frequency (f)• Wave equation

V = λ x f

Relationship between wave properties

• If a wave is traveling at a certain speed and you double it’s frequency, it’s wavelength will be cut in half.

• If you cut a waves frequency in half, the wavelength will double.

• Means wavelength and frequency are inversely related.