PASCO WA-9899 Ripple Tank System - Manual (Page 15)

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M o d e l N o . W A - 9 8 9 9 E x p e r i m e n t 2 : R e f r a c t i o n
15
Experiment 2: Refraction
Purpose
The purpose of this activity is to show how waves change direction as they pass from
one region to another where the wave speed is different.
Theory
As a wave travels from one medium to another where the wave
speed is different, the wave bends to a new direction. If the wave
slows down, the wave will bend toward the normal of the interface
between one medium and the other as shown in Figure 2.1. This
bending is called refraction.
Setup
1. Mount the light source onto its rod at the back edge of the rip-
ple tank.
2. Pour a small amount of water into the tank and adjust the feet on the legs of the
tank to level the tank.
3. Place the trapezoidal refractor in the middle of the tank and add about 700 mL of
water, or enough water so that the water level is at the top edge of the refractor.
4. Use a rod and base to support the ripple generator and position the generator over
the midpoint of one side of the ripple tank. Plug the light source into the ripple
generator and connect the ripple generator to its power adapter.
5. Connect the plane wave dipper to the ripple arms. Adjust the ripple generator
until the bottom of the plane wave dipper is barely in contact with the surface of
the water.
6. Place a sheet of paper directly under the ripple tank so you will be able to sketch
the images of the waves that are projected onto the sheet by the light source.
Equipment from Ripple Tank System
Ripple Tank Ripple Generator and Light Source
Trapezoidal Refractor Plane Wave Dipper
Concave Refractor Ruler
Convex Refractor
Other Equipment and Materials
Large Rod Stand (ME-8735) Paper (about 40 cm by 40 cm)
90-cm Rod (ME-8738)
Figure 2.1: Refraction
medium #2
medium #1
interface
Tip: Make sure that
the plane wave dip-
per is in contact
with the water
evenly over its
length.
Water appears to
curve upward on the
sides of the plane
wave dipper