We’ve done a lot of classic science fair projects and a lot of quick STEM activities.
This time, we thought we would combine the back to school season with the science of light refraction and complete our own bending pencil experiment.
The pencil in water experiment is a lesson in light refraction. It’s a fun experiment to teach kids how light moves in waves just like sound.
You can’t see light move in waves until something blocks the light (the water) and bends the light.
This simple refraction science experiment is super simple, but there is a lot of science behind the magic.
Keep reading to learn how to put together your own bending pencil experiment.
Bending a Pencil Lesson Plan
Want to turn the bending pencil experiment into a complete lesson? Just add these elements to your science time:
Experiment Variations
Any science experiment should include variations on the “right” answer.
For the refraction science experiment, you might try sticking the pencil in other types of liquids to see if they also bend the light.
Try using syrup, oil, or milk for the experiment.
You can also test the activity with other types of materials. Can you get a pen to bend? What about something that is already bent? Can you make it appear straight?
Science Explanation
Before or after doing the experiment with the kids, have a period where you discuss the science behind the lesson.
This is a good resource for learning about the science of light refraction.
Depending on the age of the children doing the experiment, you can dive deep into the science or just skim the basic principles.
Data Recording and Analysis
All good scientists know that data recording and analysis is crucial to any scientific discovery.
What this looks like will depend on the grade level of the child.
A young child might draw a picture of the results and write a word or two.
Older kids can dive into the math behind light refraction and can discuss the formula for the speed of light.
You may also want to check out our extensive lists of other STEM activities and science experiments for kids!
Bending Pencil Experiment Science Explanation
Light travels slower through water than air. When light enters the water, it slows down and changes direction.
Then, as soon as the light waves reach the end of the water, they speed up again.
This makes the image of the pencil appear broken because you’re viewing the pencil through the slower light waves in the water, and the faster light waves through the air on the part of the pencil outside the water.
When you look at the pencil from the side, the part above the water you can view light as it travels directly from your eye to the pencil.
But the part of the pencil in the water light travels from your eye, through the jar, through the water, and then out of the air.
This causes the light to refract because it is hitting different densities of materials.
Because of this, the image gets distorted and the pencil looks broken.
Pencil Experiment Supplies
You need just a few supplies for the refraction science experiment, which makes it even easier to do!
Each student will need one pencil and a jar half full of water for this experiment.
You can also have your students do the activity in groups of 3-4.
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You will need:
The Mason Jar Scientist: 30 Jarring STEAM-Based Projects
12 Ball Mason Jar with Lid – Regular Mouth – 16 oz by JardenDixon Ticonderoga Wood-Cased #2 HB Pencils, Box of 96, Yellow (13872)
How to Do the Pencil in Water Experiment
This experiment is so easy to do!
You’ll need to fill your jars halfway with water.
Place a pencil inside the jar.
Rotate the jar until the pencil appears broken.
Discuss the concept of light refraction with the kids.
Test out light refraction with other mediums, such as oil or syrup.
Do the results stay the same? Are they more dramatic?
Have the kids record their results on their science worksheets .
More Quick STEM Activities
Amazing Hot and Cold Water Density Experiment
Leak Proof Bag Science Experiment