Waves Turk 1

Waves A wave is a disturbance that carries energy through matter or space. 2

Mechanical Waves Most waves must travel through matter The matter through which a wave travels is called the medium. 3

Electromagnetic Waves The one wave that does not need a medium. Light waves are called electromagnetic waves 4

The terms light and light waves can refer to any type of electromagnetic wave – not just visible light 5

Waves & Energy Waves carry energy They can do work They move objects 6

Waves & Vibrations Most waves are caused by vibrations. This vibration involves transformations of energy much like those in a swinging pendulum 7

As waves carry the energy, the particles in the medium move As waves carry the energy, the particles in the medium move. The direction of this motion determines whether the wave is a transverse or a longitudinal (compressional) wave. 8

Transverse Waves Waves in which the motion of the particles is perpendicular to the motion of the wave. 9

Longitudinal Wave Waves that cause the particles in a medium to travel parallel to the direction of the wave motion. 10

Transverse waves – water waves, electromagnetic waves Longitudinal waves – sound waves, springs 11

Surface Waves: A combination of transverse and longitudinal Occur at the boundary of two mediums (ex – water and air) The particles of a surface wave move both perpendicular and parallel to the direction that the wave travels. 12

Crest & Trough Crest – Highest point of a wave Trough – lowest point of a wave. Crest Trough 13

Amplitude The distance a wave moves from its resting position Resting 14

The larger the amplitude – the more energy is carried by the wave. Amplitude cont. The larger the amplitude – the more energy is carried by the wave. 15

Wavelength The distance from any point on one wave to a corresponding point on an adjacent wave. Usually crest to crest or trough to trough Wavelength 16

The symbol for wavelength is λ (the (Greek letter lambda) Wavelength cont. The time it takes for one full wavelength of a wave to pass a certain point is called the period. The symbol for wavelength is λ (the (Greek letter lambda) 17

Period The time required for one cycle, a complete motion that returns to its starting point. Any periodic motion has a frequency

Frequency the number of full wavelengths that pass a point in a given time (rate). The greater the number of waves per second, the higher the frequency – the more energy carried by the wave. The symbol for frequency is ƒ. 19

Frequency Equation 1 Frequency = period ( ) or f = T Cycle second Frequency is measured in hertz (Hz). 1Hz = 1 wave per second. 20

Wave Speed v = f x λ How fast a wave moves. d S = t speed = frequency x wavelength Speed = x = or v = f x λ 1 distance distance time 1 time 21

Symbols V = speed f = frequency unit = Hz λ = wavelength unit = m (meter) 22

Wave speed depends on the medium. Wave Speed cont. Wave speed depends on the medium. In a given medium the speed of waves is constant. 23

Kinetic Theory and Wave Speed In a solid, molecules are close together so waves travel very quickly through solids 24

In a liquid, molecules are farther apart but can slide past one another so waves do not travel as fast as in a solid. 25

In a gas, molecules are very far apart so a molecule has to travel far before it hits another molecule – so waves travel slow in gases. 26