Lab 3 – pg 1
Physics 123
Identification Number _________________
Lab #3
Dispersion
In this lab you will use a computer simulation to study how wave packets propagate in linear
media. You will study both nondispersive media in which sinewaves of all wavelengths travel
at the same speed (like, for example, light traveling in a vacuum) as well as dispersive media
(like light traveling through a piece of glass, electron quantum waves traveling through space,
and just about every other real system).
The first step is to go to the class website and click the “Lab 3  Dispersion” link. You can run
the applet and get additional help there. Once the applet is running, you should see a screen with
two graphs and some text. The next step is to click on the red “get help” button in the upper left
hand corner and read the instructions for the software. Before proceeding, you may want to play
with the program for a bit to make sure that you understand how it works.
Uncertainty
First let’s explore the uncertainty which is inherent in waves. To do this, first click
on “Reset All.” In the upper graph you should see a depiction of a Gaussian wave packet (a little
“burst” of a sinewave with a Gaussianshaped “envelope”). In the lower graph you can see the
spectrum of the pulse (the amplitude of each of the sine waves which the computer added
together to make the wave packet in the upper graph). On the far righthand side of the program
the computer displays
Δ
x
; (the standard deviation of the pulse in space),
Δ
k
(the standard
deviation of the pulse’s spectrum), and the product of the two.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Winter '09
 Physics, Wavelength, pulse, group velocity, Δk, dispersion relation

Click to edit the document details