CHAPTER 14

Wave Properties

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 pointCrest=highest pointWavelength (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: 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 0.271 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=.00521 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 wavePhet

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.