Bend Light with this Water Trick

Bend Light with this Water Trick

You won’t believe your eyes with this week’s experiment! It is all about light! Light can behave in different ways; it can reflect, refract, or be absorbed.

In this experiment, you can teach your kids about refraction which is the bending of light. When light moves through different, see-through (transparent) materials, it bends! Light is forced to speed up or slow down and the change in speed and angle of the light beam causes it to refract. Rainbows form because of a combination of reflection and refraction in a raindrop!

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What you need

A clear glass cup

Another cup filled with water

A small piece of paper with two arrows drawn going in two different directions (one arrow faces right, the other faces left)

What you do

  1. Have your kids look at the colored arrows and note what direction they are pointing
  2. Put your arrows behind the empty clear glass. Hold it a few inches away (you will need to play with the distance)
  3. Get eye level with the glass, holding the paper behind it and pour in your water, filling the glass completely
  4. Have your kids watch as you fill the glass
  5. Watch carefully as the arrows REVERSE once there is water in the cup!

You might not believe it, but the glass and water force the light to bend and the arrows look reversed to our eyes

Here is what is happening

Light is traveling from the air, through the glass, through the water, through the glass, and into the air again. This forces the light to change speed and refract (or bend). What is making the arrows look like they change direction is the water! The water in the cup is acting like a magnifying glass forcing the light bend and come together into a focal point. Past the focal point then the rays of light pass each other so the light that was on the right is now on the left and vice versa, this makes the arrows look reverse to our eyes!

We can connect the way light behaves in the atmosphere with this experiment. If you have ever seen a double rainbow, you’ll notice the secondary bow has colors that are reversed. For a rainbow to form, the light is refracted and reflected in the raindrop. A double rainbow happens when the light is reflected twice.

Don’t forget to share your kids’ reactions with us when you try this out!