Polarized Images
Safety Warnings
Warning: Overhead Projector Heat
Purpose
Birefringent image plates placed between crossed polarizers on an overhead projector display vivid interference colors that change dramatically when the analyzer is rotated. Demonstrates polarization, birefringence, and wavelength-dependent interference in a visually spectacular way.
Figure 1:
Iris image (made from layered Scotch tape) between crossed polarizers. Different tape thicknesses produce different colors; colors invert when the analyzer is rotated 90°.
Figure 2:
The same iris without crossed polarizers — colors shift to complementary hues. The layered Scotch tape strip construction is visible.
Figure 3:
Commercially produced birefringent butterfly (probably thin mica layers) between crossed polarizers. Cyan and pink interference colors appear.
Figure 4:
The butterfly with analyzer rotated — colors invert to complementary orange and green. The circular mount frame is visible.
Figure 5:
Emoji face made from two layers of Scotch satin-finish tape at 45° to each other. At this orientation, a happy grinning face appears.
Figure 6:
Rotating the plate 45° changes which tape regions transmit light, producing a completely different facial expression.
Figure 7:
Further rotation produces yet another expression — a winking face with tongue out. Each orientation activates different tape regions.
Figure 8:
The three image plates: tape-constructed iris (left), commercially produced mica butterfly in circular mount (center), and tape-constructed emoji face between glass with blue tape edges (right).
Equipment
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