PASCO WA-9899 Ripple Tank System User Manual
Page 17
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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
17
Part 2: Refraction Using Curved Refractors
Procedure
1.
Replace the trapezoidal refractor
with the convex refractor, placing
it in the middle of the tank with
the straight side parallel to the
plane wave dipper and about 5 cm
from the dipper as shown in Fig-
ure 2.3.
2.
Turn on the ripple generator and
light source. Trace the position of
the convex refractor on the paper
below the ripple tank.
3.
Trace the pattern of plane waves
as they move from the plane wave
dipper over the convex refractor.
4.
Use the ruler to measure the focal length of the convex ‘lens’. This is the distance
from the center of the lens to the point where the refracted plane waves appear to
converge (come to a focus).
5.
Replace the convex refractor with the concave refractor and trace the new pattern
of the plane waves as they move from the dipper over the refractor.
Data Analysis
1.
Use the ruler to sketch three rays that represents the direction of motion for three
sections of the plane waves from the dipper as they pass over the convex refrac-
tor. Draw one ray for the wave fronts that move over the upper third of the con-
vex refractor; draw a second ray for the wave fronts that move over the center
third of the refractor, and draw a third ray for the wave fronts that move over the
lower third of the refractor.
2.
Repeat the sketching of rays for the wave pattern of the waves moving over the
concave refractor. Draw one ray for the wave fronts that move over the upper
third of the concave refractor; draw a second ray for the wave fronts that move
over the center third of the refractor, and draw a third ray for the wave fronts that
move over the lower third of the refractor.
Questions
1.
What happens to the direction of the rays for the wave fronts of the plane waves
as they move over the concave refractor?
2.
Do the refracted waves from the concave refractor appear to converge or
diverge?
Figure 2.3: Position of Convex Refractor