12/8/08
Post date: Dec 07, 2008 8:25:4 PM
Bell Activity: What is a wave?
"The Wave"
Students line up and do "the wave" (like at a stadium)
One person starts "the wave" - this initial event is called a disturbance
The initial disturbance moves down the line of people; we say the disturbance propagates
Each person in line does what the last person did
Each person does their part after the person next to them does theirs.
There is some material that the wave travels through, we call it the medium (here the students were the medium)
How quickly the wave moves down the line of people is called the wave speed
Types of waves
Transverse waves - particles move perpendicular to the wave's motion (like we did earlier, where the wave moves down the line of people, but each person moves up and down)
Examples: waves on a spring, "the wave", light waves
Longitudinal waves - particle move parallel to the wave's motion
Examples: leaning wave, spring when you compress a section and let it go, sound waves
Wave pulse - one disturbance is sent down the line
Traveling wave - repeated disturbance is sent down the line
Standing wave - when the medium has a boundary at one end, the wave may be reflected in such a way as to make the wave look like it is standing still (click on the image below to see this)
Anatomy of a wave
Period (T) - the time for a particle's motion to repeat - measured in seconds
Frequency (f) - how many cycles occur in one second - measured in Hertz (hz)
Equilibrium - the resting position of the medium
Peak - the highest point on the wave
Trough - the lowest point on the wave
Wavelength (lambda) - distance between like points on the wave (e.g. peak-peak or trough-trough) - measured in meters
Velocity (v) - how quickly the wave moves down the line - measured in m/s
Amplitude (A) - a wave's maximum distance from equilibrium - measured in m
Equations
Frequency and Period
are the inverse of each other
f = 1/T
The wave equation
relates wave speed, frequency, and wavelength
v = f * wavelength
Page 293: 1-4
Remember that v=d/t
The speed of light is approximately 3.00 x 10^8 m/s.