Ruler Changes Size
- Tall empty clear glass
- Cooking Oil
- Rubbing Alcohol
Step 1 – Pour water into a tall clear glass. Fill it about 1/3 of the way full
Step 2 – Next, carefully pour in cooking oil into the glass until the glass is a little less than 2/3 of the way full.
Step 3 – Slowly pour rubbing alcohol into the glass until the glass is almost full of liquid.
Step 4 – Wait for about 30 seconds to allow the liquids to settle. You will notice three layers of liquid, first water at the bottom, then cooking oil in the middle and finally rubbing alcohol at the top.
Step 5 – As you observe the ruler in the glass, first notice that the ruler appears to get wider as soon as it enters the liquid within the glass cup. Immediately remove the ruler from the liquid to show that it really isn’t wider, it just appears to be when observed in the liquid.
Next, place the ruler back into the liquid and look very closely through the side of the cup. As you look closer, you will notice that the width of the ruler appears to change depending on the liquid it is in.
How Does the Experiment Work?
When the ruler is placed in the liquid it appears to get wider, but once we remove the ruler we see that it isn’t really wider at all. This is because of refraction.
As light travels through a given medium, it travels in a straight line. However, when light passes from one medium into a second medium, the light bends.
Refraction is the bending of light as it passes from one medium into another (i.e. Air to Water, Water to Air).
When we look at the portion of the ruler that is outside the glass of water, light from the ruler travels in a straight path to the eye. However, when we look at the ruler within the water, the light is refracted as it passes from the liquid into the air. This causes the ruler to look wider even though it truly isn’t.
Furthermore, the type of liquid impacts refraction. That is what the ruler looks even wider when observed in the cooking oil than when observed in the water or rubbing alcohol.
More Fun Experiments that Show Refraction
Why does the Arrow Change Direction – Watch in amazement as the arrow to changes direction.
Can Water Bend a Straw – Another simple and fun experiment that shows refraction in action.
I hope you enjoyed the experiment. Here’s some printable instructions.