PASCO OS-8515C Basic Optics System - Manual (Page 63)

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M o d e l N o . O S - 8 5 1 5 C T e a c h e r ’ s G u i d e
63
Notes on analysis:
1. One way to find n
acrylic
is to plot sin(
θ
i1
) versus sin(
θ
r1
)
and find the best-fit line. The slope of the line is equal to
1/n
acrylic
. Using this method and the data above,
n
acrylic
= 1.498 for Trial 1.
2. For Trial 2, n
acrylic
is the slope of sin(
θ
i2
) versus sin(
θ
r2
),
thus n
acrylic
= 1.50.
Answers to questions: 1. Yes, the law of refraction is the
same for light going in either direction between the two media.
2. Yes, the principle of optical reversibility holds for both reflection and refraction, thus the law that the angle of
incidence equals the angle of reflection.
Experiment 11: Dispersion
Typical results from analysis:
1. Color separation was first noted at about 40°, although it may be noticeable before then depending on the
light in the room.
2. Maximum separation occurs at about 85°; beyond that the violet is totally internally reflected.
3. In order, the colors seen are: red, orange, yellow, green, cyan, blue, violet (though not all colors may be
resolvable depending on the room light).
4. With an incident angle of 40°, the violet refracted at 76° and the red at 73°; therefore n
red
= 1.488 and
n
blue
= 1.510
Experiment 12: Focal Length and Magnification of a Thin Lens
Note on equipment: Provide students with the +100 mm mounted lens. Cover the focal length indicated on
the label. Other converging lenses will work, but you may have to modify the light source-to-screen values given
in Table 12.1.
Part 1: For a distant object, 1/d
o
approaches zero, therefore the image will form clearly with a lens-to-screen
distance of d
i
= f ≅ 10 cm.
0.0 0.2 0.4 0.6 0.8 1.0
0.0
0.2
0.4
0.6
0.8
1.0
Trial 2
slope = 1.498 ± 0.009
Trial 1
slope = 0.666 ± 0.013
1/slope = 1.50 ± 0.03