Optics Lab

Topics: Geometrical optics, Total internal reflection, Optics Pages: 9 (1767 words) Published: May 22, 2013
Optics Lab:

Mirrors and Lenses

Theodore Gotis

Oakton Community College
(revised 7/21/11 J)

I. Introduction and Objectives

II. Equipment Needed

Ray BoxConcave LensCompass

Plane MirrorConvex LensProtractor

Concave MirrorPrismRuler

Convex MirrorWater Tray

III. Theory

Ray diagrams

Focal length
Radius of curvature
Law of reflection
Snell’s Law (Refraction)
Total Internal Reflection

IV. Experimental Procedure

A. Plane Mirrors

1. Use a ruler to draw a straight line on one side of a sheet of paper near the center, then draw a perpendicular line through the center of the first line. 2. Line up the front edge of the plane mirror with the straight line so that the perpendicular is at the center of the mirror.

Figure 1: Plane Mirror

Ray Box

Incident Ray Plane Mirror

Concave Mirror ( Perpendicular to the Plane Mirror

Reflected Ray

3. Using the concave mirror from your mirror and lens kit, cover up all but one of the rays coming from the ray box. 4. Now aim this single beam of light at an angle ( between 30(and 60( from the perpendicular to the plane mirror, and trace the incident and reflected beams of light with a pencil. 5. Using a protractor, measure the angle ( between the incident ray and the perpendicular to the plane mirror. Do the same for the reflected ray. 6. Now repeat Steps #4-6 for two more incident beams of light between 10( and 80(

Data Table 1: Plane Mirror

|Angle of Incident Ray |Angle of Reflected Ray | | | | | | | | | |

7. Write an equation on the line below describing the relationship between the angles of the incident beam and reflected beam of light from the perpendicular to the plane mirror. (Yes, it is as simple as you think.)


B. Spherical Mirrors (Funhouse Mirrors)


Concave spherical mirrors behave very much like the mirrors used in reflecting telescopes, they direct rays of light to a focus in front of the mirror. Reflecting telescopes actually use parabolic mirrors to assure that all the rays are directed to the same focus. Spherical aberration occurs when all the rays are not directed to the same focus. Guess which type of mirror is known for spherical aberration, spherical mirrors or parabolic mirrors?

1. Trace the shape of a concave mirror on one side of a sheet of paper using the mirror provided. Then line up the mirror on the curve you traced just as you did with the plane mirror. 2. Place the lens that is convex on one side and flat on the other at the front of the ray box so that the rays leaving the box are parallel to one another. Then aim the rays at the concave mirror so that all the rays converge at the same focus. (Remember that you need to focus on the rays in the center portion on the mirror because in general not every ray running parallel to the principal axis will be reflected through the same focal point. Most incoming parallel rays will converge to the same point only when the arc length of the mirror is smaller than the radius of curvature or if the mirror is parabolic.)

Figure 2: Concave Mirror

Ray Box Concave Mirror


3. Trace all incident and reflected rays, indicating the direction of the rays...
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