Name
Period
Date
CONCEPTUAL PHYSICAL SCIENCE EXPLORATIONS
Wques and. Sound: Two Types
of WaDes-Tronsaerse and Longitudinal
Water Waues in an Electric Sink
Purpose
In this activiiy, you will observe and control ruaves in a dpple tank simulator 1o l€arn the
basics of wave m€chanics.
Required Equipment and Supplies
PhET stmulator: "Wave Interference" (from http://phet.colorado.edVindex.php)
Discussion
The ripple tank was an effective (though
cumbersome) device used for demonstrating
and exploring wave phenomena. lt res€mbled
a small glass table ri,tth raised edges. Waler
was poured onto the table and kept from
spilling by the raised edges. Typically, a
strong point light source was placed above
the tank and shadows of ripples could be seen
below th€ tank. A small ball attached to z,
motor bobbed in and out of th€ wat€r to
make waves with consist€nt amplitud€ and
wavelength.
Figure 1. A ripple tank
A vari€ty of wave phenomena could be demonstrat€d using the ripple tank. This activily
uses a ripple tank simularor, so you'll b€ able to inv€stigate waves without the water.
Procedure
Pari A: Crests and Troughs
Step l: When th€ simulator opens, you will
see a faucer dripping water into a large sink.
The drops cr€at€ ripples in th€ water in the sink.
St€p 2: Locate the "Rotate View" slider in the control panel on the right side of the
windoe. Drag the sltder to the right. Doing so rotates your view of the sink from a top view
Step 3: Locate the "Pause" button at the bottom of the window. Try to pause the
animation when the water under the faucet dses to its highest point (close to or touching ihe
taucer. itsel0.
Step 4: Locat€ th€ "Show Gmph" button below the blue waier of the dpple tank. Click il to
activate the graph. Notice that the graph and the side vi€w of the water match each other-
Step 5: Slide the "Rotate View" slider back to the left so that it shows the toD view of the
.
115 .
a. ln the spaces below, sketch the wave pattem as lrom the toD and from the side.
Side View (Oroph)
\
b. In borh views (side vi€w and top view), Iab€l a
cre.r
and a
trough.
c. In both vi€ws, label one wavelenglh.
Parr B: Ampntude
Step 6r Pause th€ animation. Locate the frequency slider below the fauc€t. Set the
frequency to its maximum value by moving the slider all the way to the dghr. Restari the
animation by clicking the on-screen PlaV button.
Step 7: Locate th€ amplitude slider. SIide it to various postttons (to the left and right) and
observe the effect this has on the simulation.
a. Does a change ln amplitude result in a change tn the size of the water drops?
If so, how?
b. How ar€ high-amplitude waves different from low-amFlitud€ waves?
c. Review your sketches (side view and top view) of the wave above. Label rh€ amplitude oI
d. Which view-side or
€.
top-ts
better sufted for labeling the amplitud€? Explatn?
What-tf anything-happens to the amplttud€ oI each wave
as ft gets farther away
lrom
Part C: Frequency
Step 8: Pause the animation set the amplitude to its maxtmum value bv moving rhe slider
all the way io the right. Restart th€ animation bv clicking the on-screen Plav button
Step 9: Move the frequency slider to various positions (to rhe left and right) and observe the
effect this has on the simulation
a. How are high-frequency waves different from low-frequencv waves? (t ''hat is different?)
b. How are high-frequency wav€s the same as low-frequencv waves? (What isn't different?)
c. Two stud€nts disagree about an observed difference b€tween high-frequencv waves and
low-frequency wav€s. One says high-frequ€ncy waves are faster than low-frequency waves'
the other ctaims boih waves have the same spe€d What do vou think?
d. What is the relationship between the frequencv (0 of rhe wave source (the ddpptng faucet)
and the wavel€ngth (L) of the waves?
Direct proportionality: l'
-
f. The wavelength increases as the frequency increases'
-
Inverse proportionality: i"
'
1/f. The wav€lenglh increases as the frequency decreases'
No apparent relatlonship The wavelength doesn't appear to be related to the fr€quencv'
from
e. What-if an!'thtng-happens to the wavelength of each wave as it gets farther awav
Summing Up
f.
examin! the illustrations below. Each repr€sents a rippl€ tank wave Some are side
views; some ar€ top vlews. Describe the amplltude of ihe wave and the fr€que-ncv of tls
source by usiDg th€ terms "high" or "lo\.v. Please examine all the patterns betore
recording vouirtescriptions (Hint: waves a-d are all differenl frcm one another')
amplitude
.
117 .
b.
amplltude
c.
-amPlttude
mplitude
d.
2. What single aspecr of a w?ve does its amplitude best repres€nt?
speed
3.
wavelength frequency - energv -
period
a. Which control on a music player or television 6€t allows you to increase or decreae the
amDlttud€ of the sound waves that come out oI lt?
Recall whar happ€ns ro the amplitude of a wave as the wave gets farther from the source'
Imagine a portable music player plaving music in a large, open field At some dtslance from
the plaver, the amplitude of the sound waves dimlnishes to zero and the sound cannot be
heaid. Consider the three-dimensional space in which the sound can be heard'
b. How mlght you increase that space, and what is thrce-dimenslonal space caled (in
geometry)?
c. Rippl€ tanks are used to oberve two-dimensional waves. What should be the name of
the amDlitude conrrol for two-dimensional waves?
\
.
118 .