 # Wave Properties Chapter 14.

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Wave Properties Chapter 14

Types of Mechanical Waves
Longitudinal Waves Transverse Waves

Mechanical Waves Wave pulse= a single bump or disturbance that travels through a medium Periodic Wave= a wave that moves up and down at the same rate Transverse Wave =a wave that vibrates perpendicular to the direction of the wave’s motion Disturbed in the vertical direction, but the pulse travels horizontally

Mechanical Waves Longitudinal Wave= the disturbance is in the same direction as, or parallel to, the direction of the wave’s motion Surface Wave= a wave that has characteristics of both transverse and longitudinal waves

Measuring Waves Longitudinal Wave

Measuring Waves Transverse Wave

Measuring Waves Speed= displacement of the wave peak divided by the time internal Trough= lowest point Crest=highest point Wavelength (λ)= the shortest distance between points where the wave pattern repeats (crest to crest OR trough to trough) Amplitude (A) = the maximum displacement of the wave from its position of rest, or equilibrium Depends on how it is generated but NOT its speed

Measuring Waves Phase= any two points on a wave that are one or more whole wavelengths apart are in phase Period (T)=the amount of time required for an object to repeat one complete cycle of motion Frequency (f)= the number of complete oscillations that a wave makes each second, measured in Hertz (Hz)

EQUATIONS!!!!! Frequency of a Wave: Wavelength : λ=v/f f=1/T
Frequency is equal to the reciprocal of the period Measured in Hertz (Hz) Wavelength : λ=v/f Wavelength is equal to the velocity divided by the frequency Measured in meters (m)

Practice Problem A sound wave has a frequency of 192 Hz and travels the length of a football field, 91.4m, in s. What is the speed of the wave? What is the wavelength of the wave? What is the period of the wave? If the frequency was changed to 442 Hz, what would be the new wavelength and period? ANS: v=337m/s λ= 1.76m T= s

Wave Behavior

Waves at Boundaries Speed of a mechanical wave depends only on the properties of the medium it passes through What would happen when a wave passes from one medium to another? Pulse from the wave in the first medium continues into the new medium at the specific speed Incident wave= a wave that strikes the boundary between mediums Reflected wave= the returning wave Phet

Superposition of Waves
Principle of superposition= the displacement caused by two or more waves is the algebraic sum of the displacements caused by the individual waves Translation= two or more waves can combine to form a new wave Interference= the result of the superposition of two or more waves

Interference Constructive Interference= When the crest of one wave overlaps the crest of another their individual effects add together to produce a wave of increased amplitude Destructive Interference= When the crest of one wave overlaps the trough of another wave their individual effects are reduced

Standing Wave Standing wave= a wave that remains in a constant position This phenomenon can occur because of constructive interference caused by the medium is moving in the opposite direction to the wave Or… it can arise in a stationary medium as a result of interference between two waves traveling in opposite directions. Animation

Standing Waves A node is a point along a standing wave where the wave has minimal amplitude An antinode is a point where the amplitude of the standing wave is a maximum These occur midway between the nodes.