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Geometrical Optics

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This lab looks at three situations that can be analyzed using the techniques of geometrical optics: (1) ray deviation by a prism, (2) ray deviation by a spherical drop and (3) refraction at a spherical surface. The specific lab activities are listed below.

For the ray deviation by a prism, the students measure the index of refraction of the prism by measuring the angle of minimal deviation.

For the ray deviation by a spherical drop, the students locate the class 3 ray and use it to measure the critical impact parameter, the angle of minimal deviation and the rainbow angle. These measurements are repeated for the class 4 ray (the secondary rainbow).

For the refraction at a spherical surface, the students measure the focal length of a water filled lens as a function of h, the distance of the incoming ray from the axis of the lens.

In all cases, the experimental results are compared to theoretical predictions. With careful alignment of the systems, experimental results will be within 1-2% of the theoretical values.

Course Level


Student Handouts


Number of set-ups available: 10

Per lab station:

1 He-Ne laser
1 two layered optical bench with swivel mirror
1 two mirror set
1 roll of masking tape
1 meterstick
1 ruler
1 equilateral prism
1 glass dish
1 index card/perpendicuolar line drawn on it
1 cylindrical lense (beam spreader/brass base)
14" 10 div/in graph paper
11" 10 div/in graph paper



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