Lecture Demonstrations Laboratory

The Demonstrations Manual

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Geometrical Optics: Speed of Light; 1/R^2 Demonstrator; Blackboard (or Elmo) Optics; Confocal Mirrors; Concave Mirror; Light The Match; Disappearing Beaker; String Model of Refraction; Total Internal Reflection; Steal the Light; Light Pipe and Fiber Optics; Water Light Pipe; Thin Lenses with Objects
Diffraction
Interference
Color
Polarization
The Eye

Light The Match

Purpose:

To show that parallel rays of light entering a parabolic mirror are focused on the focal point and vice-versa.

Procedure:

Place the lamp at the focus of one mirror and insert a match in the holder attached to the other mirror. When the light is turned on the match will flame up in about 10 seconds.

Hints:

Lining up both mirrors is crucial. The easiest way to accomplish this is to use the reflection in the mirror itself. For example, to make sure the match head is lined up properly, look beyond the match head at the reflection in the mirror. The match head should be centered in the image of the opposing reflector. Use the same method for lining up the other mirror.

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Equipment:

Lamp
Matches
Stand
Large Concave Mirrors