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How to make two combs wriggle

Light: Demonstrating interference lines with light through repetitive patterns

Sunshine State Standards: SC.H.1.2 SC.H.2.2

Materials:

• Identical Pocket Combs
• Transparencies and prints to make patterns

To Know:
When you look through one chain-link fence at another, you sometimes see a pattern of light and dark lines that shifts as you move. This pattern, called a moiré pattern, appears when two repetitive patterns overlap. Moiré patterns are created whenever one semitransparent object with a repetitive pattern is placed over another. A slight motion of one of the objects creates large-scale changes in the moiré pattern. These patterns can be used to demonstrate wave interference..

To Do and Notice:

• Hold two identical combs so that one is directly in front of the other and they are about a finger-width apart.
• Look through the teeth and notice the patterns of light and dark that appear. This is a moiré pattern.
• Now slide the combs from side to side and watch the moiré pattern move.
• Now rotate one comb relative to the other and notice how the pattern changes.
• Now separate the combs by about 8-10 inches and repeat the movements

Now try this:

• Place one of the transparencies from the pattern of lines or circles provided with this Snack on top of a print
• As you move them apart and then together, look through at the patterns created. The moiré pattern consists of radiating dark and light lines. You can see different effects by rotating or sliding or lifting the transparencies.
• Now try this with a different print..

Learn more…

Developed by the GE Volunteers in partnership with the Museum of Arts and Sciences (MOAS) – Daytona Beach, FL