Optics Magic

Overview: Refraction and Persistence of Vision are two optical phenomenon we can use to create “magic”

Refraction is the bending or change in direction of light as it passes from one transparent medium to another (e.g., air to water or glass). This phenomenon occurs because light travels at different velocities in different materials. We can use refraction to create the illusion of an optics magic show.

Persistence of vision is the optical illusion that occurs when the visual perception of an object does not cease for some time after the rays of light from it have ceased to enter the eye.

Supplies: Magic trick 1: Small jar, water beads, small colored toy, water

                Magic trick 2: Coffee mug, coin, water

                Magic trick 3: Clear glass, pencil or pen, water

                Magic trick 4: Screwgun, color wheel

                Magic trick 5: Praxinoscope

                Magic trip 6: Thaumatrope

Objectives: Show how each magic trick deceives us into thinking one thing, but we see another. Understand how refraction and persistence of vision makes these magic tricks possible.

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Setup:

• No particular setup necessary, other than putting out all the tricks on the table

How to run the demo:

• Adjust the lasers until the spots overlap on the screen and form a yellow spot

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What’s Happening?

This form of color mixing is called additive mixing, where the combination of primary colors (red, green, and blue) creates white light. When you combine two of the three primary colors you can create magenta, cyan and yellow. Take a red and green laser to combine their light together and make yellow spot. Note that this is different than subtractive mixing; we experience subtractive mixing with paint and inkjet printers, where the combination of primary colors (cyan, yellow, magenta) creates black paint.

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