Light can play tricks on you! Physicists study how light helps us see everything around us!
Learn how to use light to create a magic trick of your own in this fun science experiment!
Materials:
Clear glass, water, penny, hair band or rubber band, foil paper
Time Estimated:
10-15 minutes
Directions:
First, place the empty glass on top of the penny. Can you see the penny?
Now, fill the glass all the way to the top with water.
Cover the top of the glass with foil and place a rubber band around the foil to keep it secure. The surface of the water should not be visible after the glass is covered with foil. If you can still see it, add some more water.
Place the glass filled with water on top of the penny! What do you see? Can you still see the penny?
Think Like A Scientist:
Get the penny wet and then put the glass full of water on top of it. Now what happens?
What if you try the same experiment with oil instead of water? What happens? Let us know in the comments below!
How It Works:
The coin disappears under the glass due to refraction and total reflection of the light.
Refraction is the pathway of waves, light, etc. through different mediums, such as water, air, or other materials with varying density. The pathway and direction of light or waves changes as they travel through these mediums.
People see things due to light because light travels into our eyes, and the eyes send messages to the brain allowing people to know what they are seeing. Light travels through many different mediums, and the angle of refraction varies depending on the medium they travel through. Before adding water to the glass, the coin’s image can travel outside of the cup and to our eyes. However, after adding water, because the water’s index of refraction increases, it causes total refraction.
Total reflection is when a ray of light within a medium such as water or glass reflects from the surrounding surface back into the medium.
As a result, the image of the penny reflects back onto the surface of the glass of water, so we cannot see the penny.
Vocabulary:
Medium: a substance through which vibrations (waves and light) can travel
Angle of refraction: the angle between a refracted ray of light and the surface it is hitting
Index of refraction: how fast light travels through material
Looking for more fun at home STEM activities for your young scientist? Check out our workbook full of exciting science experiments and empowering activities!
