Hooked on Science: Disappearing money

Spending money isn't the only way to make it disappear.

Materials

• Penny
• Clear plastic cup
• Water

Instructions

STEP 1: Place the penny on a flat surface.

STEP 2: Place the bottom of the clear plastic cup over the penny.

STEP 3: Observe the penny through the side of the cup. Fill the cup with water and observe the penny through the side of the cup.

Explanation

When the cup is filled with water, the penny disappears. This happens because of refraction. When light bounces off an object, it reaches our eyes and we see the object. As light travels through the sides of the glass and the water, it's refracted and never reaches our eyes, which makes the penny seem to disappear.

Jason Lindsey is a science outreach educator with Hooked on Science. Check out his website hookedonscience.org for webcasts and experiments.