University of Auckland/Department of Physics/Physics 102/Description of Waves
Contents
Wave defined
A wave can be described as a repeating disturbance that travels through a medium (e.g. air) from one location to another with no net transfer of matter. However, energy is transferred.
Crest and Trough
The crest of a wave is the top of the wave and the trough of a wave is the bottom of the wave. File:CrestAndTrough.gif
Period
| The length of time for one cycle of the wave (i.e. the length of time between two consecutive crests or two consecutive troughs). |
Wavelength
The distance between two consecutive crests or troughs.
The units of wavelength are m, km, μm, nm, etc |
Wave Speed
| [math]v = {\lambda}{f} = \frac{\lambda}{T}[/math]
It has units of m/s, km/s, mm/s, etc |
The wave speed doesn't change if you change the wave length, frequency or period for a wave for a given material. This is because if one of the variables (λ, f, T) is changed, the others also change so that the velocity is the same e.g.
- if the frequency is halved, the wavelength is doubled and the period is doubled
- if the frequency is tripled, the wavelength and period and a third of their value
Speed of sound in air = 340 ms-1
Speed of light in air = 3 x 108 m s-1
-Wave velocity is related to frequency and wavelength. We can show a series of wave pulses by hitting the surface of the water in a pool many times.The pulse will move some distance before the second pulse from the original hitting site.That is referred to as the wavelength.
-The distance between pulses is λ(Greek for Lambda), and the time between pulses is the period,(T),
and the speed of the wave is the distance divided by the time, v = λ/T.
Calculating wave speed : Wave Speed=wavelength * frequency
Frequency=1/period Since the frequency and period are the inverse of each other, therefore, Period=1/Frequency.
http://www.brainpop.com/
Amplitude
The amplitude is the maximum displacement of the wave.
- Amplitude1.gif
- Calculating Wavelength of radio waves.
- The speed of light is 3.0 X 10^8 m/s. What is the wavelength of
- The radio waves emitted by KKJZ, a station whose frequency is 88.1 MHz? Solving for wavelength, we have
- Amplitude2.gif
Wave on a string example
External Resources
FYI
Heres a link thats like an online interactive textbook. Will answer any questions you might have..: http://www.glenbrook.k12.il.us/gbssci/phys/Class/waves/wavestoc.html (dhic014)
Here is a link with practice questions for wavelenght http://www.iop.org/activity/education/Teaching_Resources/Teaching%20Advanced%20Physics/Vibrations%20and%20Waves/Progressive%20waves/file_4219.doc (Jshe128)
(asch115):This is a really basic sight on waves; its basically waves for Dummies, but it gives good interactive examples to help you visualize the basic components of waves:
http://sunshine.chpc.utah.edu/labs/waves/wave_basics/waves.htm
