Demos: 7B-14 Interference Fringes in Transmission & Reflection

Two right-angle prisms are clamped together. The thin film of air trapped gives rise to interference patterns, both in the transmitted path and the reflected path. By means of an auxiliary mirror, both patterns may be displayed side by side on a screen. The colored fringes and the dark and light areas of the two patches are complementary to each other. By carefully orienting the mirror, the two patches may be superimposed and only a bright patch is seen.

Directions: The lec-demo technician should have this set up ahead of time. Darken the room and show the two patches of light on the screen. Using the thumb screw, carefully reposition the mirror so that one patch overlaps the other.

Suggestions for Presentation: Discuss carefully the reasons for the transmitted and reflected patterns being different. Especially focus on the complimentary nature of the fringes. Ask what should happen in the two patterns were allowed to overlap.


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Last Updated: May 9, 2016 11:44 AM