PASCO WA-9899 User Manual
®
Instruction Manual and
Experiment Guide
012-09956A
WA-9896 Ripple Generator and
Light Source
WA-9899 Ripple Tank System
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
About the Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
About the Experiments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Experiment 1: Reflection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Experiment 2: Refraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Experiment 3: Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Experiment 4: Interference. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Experiment 5: Image Formed by a Plane Mirror . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Experiment 6: Wave Speed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Doppler Effect Demonstration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Sample Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Technical Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
90-cm Rod,
ME-8738
(not included)
Ripple Tank System
WA-9899
Light Source
Rod
Ripple Generator
Ripple Tank Assembly
Reflector
Large Rod Stand,
ME-8735
(not included)
Dippers, Adapters,
and Actuators
Barriers
(Included but not shown: Plastic bottle of surfactant, 5 mL pipette, ruler, plastic storage box, beaker, AC adapter)
Leg
Projection
Screen
Refractors
Introduction
The Ripple T ank System consists of the WA-9896 Ripple Tank and the WA-9897 Ripple Generator and Light Source.
The table below lists the included equipment. Note: The ME-8735 Large Rod Stand and the ME-8738 90-cm Rod
shown above are recommended but not included.
This manual contains descriptions and instructions for six experiments and suggestions for an additional demonstration.
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Ripple Tank System Introduction
Included Equipment WA-9896 WA-9897 Part Number
1. Light Source 1 003-09709
2. Rod 1 648-09713
3. Ripple Generator 1 003-09724
4. Ripple Tank Assembly 1 003-09703
5. Screen Assembly 1 003-09736
6. Leg 3 648-09707
7. Standard Dipper 7 648-09712
8. Large Actuator 2 648-05471
9. Small Actuator 2 648-05470
10. Dipper Adapter 2 648-09711
11. Plane Dipper 1 003-09737
12. Curved Reflector 1 648-09820
13. Long Diffraction Barrier 2 648-09718
14. Short Diffraction Barrier 1 648-09719
15. Mini Diffraction Barrier 1 648-09717
16. Concave Refractor 1 648-09720
17. Convex Refractor 1 648-09721
18. Trapezoidal Refractor 1 648-09714
19. Bottle of surfactant
1
1650-072
20. Pipette, 5 mL 1 699-154
21. Ruler 1 699-081
22. Plastic Storage Box 1 740-177
23. Beaker, 1000 mL 1 699-197
24. AC Adapter, 15 VDC, 1.6 A 1 540-057
1
Note: The Tergitol L-62 surfactant is part number 699-023
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Model No. WA-9899 About the Equipment
About the Equipment
WA-9897 Ripple Tank
The Ripple Tank is designed to be used with the PASCO model WA-9896 Ripple Generator and Light Source. The tank is 42.5 cm by 42.5 cm by 2.5 cm with four foam “beaches”
and a 0.3 cm thick glass plate. The viewing area is 33 cm by 33 cm. The tank has an
easy-to-use drain pipe consisting of a piece of flexible vinyl plastic tubing and a tube
clamp. The tank is supported by three detachable legs with adjustable feet and comes with
a reflector and projection screen.
The ripple tank also comes with the following: ruler,
pipette, surfactant bottle, storage box, barriers (5 pieces),
refractors (3 pieces), a beaker, and a rod for supporting the
Screen
assembly
light source.
The box in which the Ripple Tank is stored has two layers.
The screen assembly, plastic storage box, rod, and beaker
Plastic
storage
box
are in the top layer; the ruler, legs, and Ripple Tank assembly are in the bottom layer. The top layer has areas for storing the WA-9896 Ripple Generator and Light Source,
Legs and
ruler
including the power adapter and cord.
Screen Assembly The screen assembly is a
reflector and a projection screen joined at one edge by a strip of flexible tape. Note:
Remove any protective coating from the reflector and the screen before using. The
reflector is aluminized acrylic. The projection screen is translucent plastic.
There are three holes along the top edge of the reflector and two strips of Velcro®
‘loop’ material along the top edge of the projection screen.
Ripple Tank Assembly The ripple tank assembly has an impact resistant
plastic frame. Below the front edge of the frame is a strip of Velcro® ‘hook’ material
that will hold the ‘loop’ material on the top edge of the projector screen. Below the
back edge of the frame are three pegs that fit into the holes in the top edge of the
reflector. The threaded hole on the top side of the back edge is for the rod that can
support the Light Source that is included in the
WA-9896 Ri pple Generator and Light Source. When
Drain hole
the ripple tank is in use, the four foam ‘beaches’
dampen the waves that would otherwise reflect and
disturb the primary wave and interference patterns.
The foam beaches are replaceable. (A variety of
replacement parts are available in the WA-9898 Ripple Tank Replacement Set.)
Projection
screen
Pegs
Rod
Ripple Tank
assembly
Velcro®
‘loop’
material
Holes
Reflector
Threaded hole
The ripple tank’s drain pipe is a piece of flexible
vinyl tubing attached below the drain hole at the back
corner of the tank. Squeeze the sides ot the tube
clamp on the drain pipe to tighten the clamp on the
tubing. Pull downward on the lip of the tube clamp to
loosen the clamp.
Strip of Velcro® ‘hook’
material (not shown)
Setup
To setup the ripple tank, screw the legs into the threaded holes on the underside near the
two front corners of the tank, and under the midpoint of the back edge. Place the ripple
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5
Ripple Tank System About the Equipment
tank on a smooth, level surface. If you are going to use the light source, screw the rod into
the threaded hole near the midpoint of the top of the back edge.
To attach the reflector and projection screen to the tank, unfold the screen assembly and
put the reflector between the two front legs. Angle the reflector upwards and guide the top
edge so that the three holes fit over the pegs that are at the back edge of the tank. Next,
raise the projection screen to the vertical position and attach its Velcro® ‘loop’ material to
the strip of ‘hook’ material under the front edge of the tank.
Apply Surfactant Before putting water into the ripple tank for the first time, pre-
pare the foam beaches, barriers, and refractors with a drop of surfactant (a nonionic wetting agent). The surfactant helps to avoid problems with the surface tension of the water.
Put a single drop of surfactant from the small plastic bottle onto the end of one finger, and
lightly rub your finger along the foam beaches. Use a single drop of surfactant to very
sparingly coat the large flat surfaces of the three refractors and the front surfaces of the
straight and curved barriers.
Tip: Note that you only need to
apply the surfactant to the
beaches, barriers, and refractors
before using the ripple tank for
the first time, or it has been
unused for a long time.
Level the Ripple Tank When you are ready to add water to the tank, squeeze the
sides of the tube clamp to close the clamp. Use the beaker to add a small amount of water
to the middle of the tank so that the water forms a circle about 10 cm in diameter. Adjust
the feet on the legs until the circle of water stays in the middle of the tank and does not
move toward any side. (An alternate method for leveling the tank is to add about 800 milliliters of water to the tank. Measure the water depth at three of the four corners of the tank
and adjust the feet on the legs until the depths are the same.)
Dampen the Foam Beaches To reduce the problem of surface tension, let the
foam beaches soak up some of the water. After putting about 800 milliliters of water in the
tank, press down on the foam and then release the pressure so that water enters the pores
of the foam rubber.
Cleanup
Before emptying the tank, remove the projection screen and reflector. Fold the screen
assembly so the projection screen protects the reflector.
To empty the tank, place a container under the drain pipe and open the tube clamp. When
the water stops flowing, raise the corner of the tank opposite to the drain hole so the rest of
the water will drain out. Leave the tube clamp in the open position.
Be careful to remove as much water from the foam beaches as possible. Press with your
thumbs against the foam to squeeze the water out. Next, press a rolled-up towel onto the
foam beaches to soak up any remaining water.
Completely dry the glass plate so that water spots won’t form on it. To clean the glass
plate or the reflector, use a soft cloth moistened with water and then dry with a clean
towel. Do not use soap or chemical cleaners.
Tip: Leave the tube clamp in the
open position after draining the tank
to avoid crimping the plastic tubing.
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Model No. WA-9899 About the Equipment
WA-9896 Ripple Generator and Light Source
The Ripple Generator is designed to be used with the WA-9897
Ripple Tank. The generator controls the included Light Source.
The Light Source uses a white light-emitting diode (LED) that
remains cool during operation and produces a bright, clear
image of the wave patterns in the ripple tank. The light can be
used as a steady source or as a strobe to ‘freeze’ the motion of
the wave patterns. The ripple generator frequency range is
from 1.0 to 50 Hz adjustable in 0.1 Hz increments, and the
generator has a digital frequency readout window that is easy
to see in dim light. The generator uses voice coil actuators to
produce the precise and quiet up-and-down motion of the rippler arms. The ripple generator has knobs for adjusting the dipper depth and amplitude and a switch for changing the phase of
the two rippler arms from zero (in phase) to 180 degrees (out
of phase).
Generator Attachments The ripple generator includes a
plane wave dipper (1), small actuators (2), dipper adapters (3), standard dippers (4), and large actuators (5). The plane wave dipper and
the standard dippers attach to the clips at the end of each rippler arm.
Use the dipper adapters to attach the small or large actuators to the
rippler arms, or to the clips on one side of the plane wave dipper. The
standard dippers can be attached to the clips at the end of each rippler
arm or to the clips on the plane wave dipper.
The standard dippers and dipper adapters are designed so that the top
‘third’ of the part fits securely into the clips on the rippler arms. The
parts fit into the clips in one way; do not force them into the clips.
The dippers and adapters are designed so that the ‘middle third’ of
the part fits into the clips on the plane wave dipper.
WA-9896 Ripple Generator (right) and Light Source (left)
with power adapter and cord
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3
2
Generator Attachments
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The standard dippers and dipper adapters can be used as ‘point sources’ when attached to
the ripple generator. In general, the higher the frequency of the ripple generator, the
smaller the point source attachment should be in order to produce the sharpest looking circular waves.
Mounting the Light Source The light source has a built-in rod clamp for
mounting the light on the rod that comes with the ripple tank assembly. Mount the light
source near the top of the rod so that the light source is at right angles to the rod and the
opening of the light source is above the center of the ripple tank.
Mounting the Ripple Generator Use the built-in rod clamp on the end of the
ripple generator to mount the generator on a 90-cm rod (ME-8738, not included) that is
supported by a large rod base (ME-8735, not included). Position the ripple generator so
that it is slightly above the midpoint of one side of the ripple tank but does not touch the
tank. Arrange the generator so that it is at right angles to the side of the ripple tank, and the
midpoint of the generator is approximately in line with the inner edge of the ripple tank.
Connecting the Power Adapter The ripple generator comes with an AC
adapter that provides 15 V DC (at up to 1.6 A). Connect the included power cord between
an electrical outlet and the AC adapter, and then connect the plug from the adapter into the
power input port on the side of the ripple generator.
Connecting the Light Source Connect the power cord from the light source
into the jack on the side of the ripple generator that is beneath ‘TO LIGHT’ on the label.
Tip: Before using the plane
wave dipper or the other dippers or the actuators for the first
time (or after a long period of
non-use), lightly coat the bottom surfaces with a very small
amount of surfactant.
Tip: Before connecting the
power adapter to the ripple generator, be sure that the
‘ON-OFF’ switch on the left side
of the generator is in the ‘OFF’
position.
Also, turn the ‘AMPLITUDE’
knob on the top of the generator
fully counter-clockwise.
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Ripple Tank System About the Equipment
Frequency
display
ON-OFF switch
Light Source jack
Power input port
Bracket
Phase switch
Ripple Generator
Dipper adjustment
knob
Amplitude knob
Frequency
knob
Rod
clamp
Dipper
adjustment knob
Dipper Adjustment The ripple generator has two dipper adjustment knobs for
making small changes to the height and orientation of the generator. You can make fine
adjustments with these two knobs to position the dippers, plane wave dipper, or actuators
in the water without moving the entire ripple generator up or down on its rod. Use the
knob on the right side of the generator to move the front end of the generator up or down.
Use the knob at the back corner of the generator to tilt the front end of the generator right
or left (clockwise or counter-clockwise).
Before making adjustments, check that the ripple generator is
parallel to the bracket when the ripple generator is mounted on
the rod. This will allow for the widest range of adjustments
when you use the plane wave dipper, standard dippers, or actuators.
It is very important that the dippers barely touch
the surface of the water in the tank. For the plane
wave dipper, it is also important that the dipper has
equal contact with the surface of the water over the
entire length of the dipper.
One way to adjust the ripple generator when it is
on the rod is to grip the rod below the rod clamp,
loosen the thumbscrew of the rod clamp, and support the rod clamp with your thumb. Gradually
nudge the rod clamp up or down on the rod until
the dippers attached to the rippler arms are in contact with the water, then tighten the thumbscrew of
the rod clamp to secure the ripple generator on the
rod.
Next, use the two dipper adjustment knobs to raise, lower, or tilt the ripple generator so the
dippers barely touch the surface of the water. When everything is adjusted, the water will
appear to ‘curve upwards’ on the sides of the dipper.
Generator parallel to bracket
Water level
Water appears to
curve upward on the
sides of the dipper
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Model No. WA-9899 About the Equipment
Amplitude Adjustment The Amplitude knob adjusts the ripple arm amplitude.
As you turn the knob clockwise, the amplitude increases. Turning the knob counter-clockwise (right-to-left) decreases the amplitude.
As a general rule, adjust the amplitude in all experiments to get a clear wave patter without
distortions.
Frequency Adjustment The Frequency knob adjusts the ripple arm frequency.
The Frequency display shows the frequency in 0.1 Hz increments. The range is from 1.0 to
50.0 Hz. When the ripple generator is first turned on, the default frequency is 20.0 Hz, a
good starting frequency for the experiments described later. Turn the knob clockwise to
increase the frequency or counter-clockwise to decrease the frequency.
Phase Switch The Phase switch at the upper right of the ripple generator changes
the phase of the two rippler arms from zero degrees (‘in phase’) to 180 degrees (‘out of
phase’). The switch can be used while the ripple generator is in operation.
Light Source Control The Light Source can be used as a strobe or as a steady
source. The controls for the light source consist of a three-position Mode switch for selecting ‘STEADY’, ‘OFF’, and ‘STROBE’, and a ‘DELTA ’ knob that adjusts the frequency of
Frequency
display
the light source when it is in the strobe mode.
DELTA Feature Normally the frequency of the light source in the strobe mode is
the same as the frequency of the ripple generator. When the frequency of the light source
is 5.0 Hz or more, you can use the ‘DELTA’ knob to increase or decrease the frequency of
the light independently of the frequency of the ripple arms. (When the generator frequency
is less than 5.0 Hz, the ‘DELTA’ knob will not change the light source frequency.) Turn the
‘DELTA’ knob clockwise to increase the light source frequency or counter-clockwise
(right-to-left) to decrease the frequency. Each ‘click’ of the ‘DELTA’ knob changes the
frequency of the light source by 0.8 Hz. The Frequency display on the top of the ripple
generator will show the ‘DELTA’ increment (e.g., 1.0, 2.0, 3.0, 4.0, or 5.0 if the ‘DELTA’
knob is turned clockwise, or -1.0, -2.0, etc., if the knob is turned counter-clockwise) for a
few moments and then change back to show the ripple generator frequency. For example,
if the Frequency display shows ‘20.0’ Hz, and you turn the ‘DELTA’ knob one ‘click’
clockwise, the Frequency display sho ws ‘1.0’ momentarily, and the light source frequency
becomes 20.8 Hz. Note that the ripple generator will continue to oscillate at 20.0 Hz.
This feature of the light source allows the wave pattern to ‘appear to move’ at a constant,
predictable speed when the light source is in the strobe mode and the light source frequency is slightly higher or lower than the ripple generator frequency.
DELTA
knob
Mode
switch
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9
Ripple Tank System About the Experiments
About the Experiments
These experiments can be done with the equipment included in the system and other items
such as a protractor, drawing compass, and paper. See each experiment for a specific
equipment list.
1. Reflection: Study the reflection of plane waves from straight and curved barriers.
2. Refraction: Study how plane waves bend when they pass from one medium to
another where the wave speed is different.
3. Diffraction: Determine how a diffraction pattern of plane waves changes as the
slit width of the barriers changes and the wavelength changes.
4. Interference: For a double-slit interference pattern, determine how the interfer-
ence pattern changes as the slit width separation and the wavelength are varied.
5. Image Formed by a Plane Mirror: Determine the position of the image formed
by a plane mirror relative to the image distance from the mirror.
6. Wave Speed: Determine how wave speed depends on frequency and on water
depth.
7. Doppler Effect Demonstration: Demonstrate the Doppler Effect by moving the
ripple generator at a constant speed in a straight line.
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