PASCO OS-8459 Beginning Optics System - Manual (Page 44)

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B e g i n n i n g O p t i c s S y s t e m T e a c h e r ’ s G u i d e
44
Experiment 3: Reflection
Part 1, typical results:
Part 1, answers to questions: 1. The angle of incidence and the angle of reflection are equal. 2. The three
colored rays are not reversed by the mirror.
Part 2, typical results:
The actual radius of both curved mirrors is about 12.5 cm.
Part 2, answers to questions: 1. The radius of curvature is twice the focal length for a cylindrical mirror.
The typical experimental results confirm this. 2. The radius of curvature of a plane mirror approaches infinity.
Experiment 4: Snell’s Law
Typical results:
Answer to question: The ray leaves the rhombus at the same angle it entered.
Experiment 5: Total Internal Reflection
Typical results:
(Step 5) Measured critical angle:
θ
c
= 41.0°
(Step 6) Calculated critical angle:
θ
c
= sin
−1
(1/n) = sin
−1
(1/1.5) = 41.8°
(Step 7) % Difference = 1.9%
Answers to questions: 1. The internally reflected ray becomes much brighter when the incident angle is
larger than the critical angle. 2. The critical angle is greater for red light. This tells us that the index of refraction
is smaller.
Table 3.1: Plane Mirror Results
Angle of Incidence Angle of Reflection
9.0° 9.2°
16.8° 16.5°
19.0° 37.8°
Table 3.2: Cylindrical Mirror Results
Concave Mirror Convex Mirror
Focal Length 6.2 cm 6.4 cm
Radius of Curvature
(determined using compass) 13.3 cm 13.2 cm
Table 4.1: Data and Results
Angle of Incidence Angle of Refraction Calculated index of refraction of
acrylic
38.0° 26.0° 1.40
51.2° 33.8° 1.40
22.0° 14.4° 1.51
Average:1.44
(4% deviation from accepted value)