What you’ll learn:
How lenses bend light and can either focus, or unfocus rays of light to a point. You’ll also learn ray tracing to see how each lens affects light.
Key takeaways:
The shape of a lens alters the way light rays pass through it. We can see how lenses focus or unfocus light through a process called ray tracing.
In a previous post, we learned about light refraction and why a prism can seperate the colors of the rainbow.
Here, we want to gain some hands on experience with light refraction. We will use an easily available acrylic lens kit and cheap dollar store lasers to learn about ray tracing as we create art!
Watch the video below to learn how to make your own optical jellyfish art, and then read on to learn more about ray tracing!
Project Ingredients:Acrylic lens set (this is the best, and cheapest, set I have found to date)Laser pointerColored pencilsPaper
What is ray tracing?
Ray tracing is a method used in physics to determine the path a ray of light will follow in a system. In this project, our system is just one single lens at a time. We take one lens, place it on our paper and trace the direction of the laser beam as it exits the lens.
Ray tracing helps people understand a system better. In this case, it helps us understand how the shape of a lens affects the direction of the laser beam on the other end. However, it can be used for things that we don’t consider light, like sound. This is because both light and sound are moving electromagnetic waves. When we talk about light we often think about only the light we can see, but this is just a tiny fraction of the electromagnetic spectrum. Everything from x-rays to radio waves and microwaves would experience the same bending when it meets a material.
Ray tracing is often used in ocean acoustics to determine where a sound came from. The varying temperatures of the oceanic water layers create a varying density that bends the sound waves as they propagate through the ocean, just as the lens bends the light as it propagates from one side to another.
What other applications involve ray tracing?
Sometimes we do things in the lab, or from textbooks that we think we won’t ever see in the real world. I remember thinking this about geometry in 9th grade but soon realized that geometry is everywhere – from how I decide what path to take through the park to determine how large of a roof to put on my gingerbread house. So, where else might you see ray tracing other than in this one specific project, or in this chapter of your science book?
We mentioned ocean or underwater acoustics above, but there are other applications of ray tracing we can talk about.
Physicists use ray tracing to determine how we can most effectively propagate radio signals through our ionosphere. Geophysicists use ray tracing to locate earthquake locations, scientists use ray tracing to figure out how to best heat plasmas, and of course, optical scientists use ray tracing to develop and predict the behavior of optical systems.
While we use computers to calculate the directions of the waves in these instances, it all comes back down to figuring out how these waves bend in a medium, just as we are determining how light is bending in our acrylic lenses.
