Getting Started

Scientist are still trying to make heads or tails of this thing called light, and near as they can tell, it sometimes interacts like a particle (like a marble) and other times like a wave (like on the ocean), and you really can’t separate the two because they actually complement each other.

Energy can take one of two forms: matter and light (called electromagnetic radiation). Matter is what stuff is made from, like a chair or a table, and we'll talk a lot more about matter when we get to chemistry.

Light is energy that can travel through space and through some kinds of matter, like glass. Another word for light is "electromagnetic radiation". Light can have high energy, lower energy, or anything in between... kind of like high energy kids (the ones who race all over the playground), lower energy kids (the ones reading a book in a corner), and kids whose energy is somewhere in the middle.

Scientists usually refer to the light energy you can see with your eyes as "visible light", or just "light", and it has middle-of-the-road amounts of energy - not high, not low. Just average. That kind of electromagnetic radiation is called "light".

Lower energy electromagnetic radiation can have wavelengths longer than a football field, and those are called "radio waves". These aren't the kind of waves that a guitar string makes when you pluck it. Radio waves are not sound waves. They are waves made out of electricity and magnetism (which we'll discuss later) that travel through space. Sound waves need something, like air, in order to travel because it does it by vibrating molecules. Electromagnetic waves work differently, but it's a little more complicated than we're going to discuss now, so just remember that light waves different than sound waves. If you've ever seen a lightning storm, you know this is true, because you see the lightning way before you hear the thunder. Which wave do you think travels faster? Light or sound?

Other examples of lower energy waves are the kind found in your microwave oven called "microwaves" (surprised?) Your TV remote uses infra-red electromagnetic radiation, which has a little more energy than microwaves.

What about high energy waves? If you've ever been curious about why the dentist puts a heavy lead apron on you before x-raying your teeth, it's because they're about to use high-energy electromagnetic radiation called "x-rays" to see through your mouth tissues to get to the bones and teeth. Since high-energy rays can destroy living tissue, you have to wear that apron. Lead stops most high-energy electromagnetic radiation in the x-ray range. Black holes, supernovae, and quasars in the deep reaches of space emit deadly x-rays and even higher-energy gamma rays.

Here are the scientific concepts:

  • Light has a source and travels in a direction.
  • Sunlight can be blocked to create shadows.
  • Light is reflected from mirrors and other surfaces.
  • The color of light striking an object affects how our eyes see it.
  • We see objects when light traveling from an object enters our eye.
  • Light can travel through a vacuum, like space.
  • Light can change speeds, but the maximum speed is through a vacuum (186,000 miles per second).
  • Prisms un-mix light into its colors or wavelengths.
  • Light changes speeds when it passes through a different material.
  • Lenses work to bend light in a certain direction, called refraction.
  • Concave lenses work to make objects smaller and convex lenses make them larger.

By the end of the labs in this unit, students will be able to:

  • Design and build a simple refractor telescope using lenses.
  • Know how to demonstrate how compound microscopes work.
  • Understand how to determine how to measure the speed of light.
  • Make observations to construct an experiment that shows that objects can be seen when illuminated.
  • Design an experiment that investigates the effect of placing objects in the path of a beam of light.
  • Differentiate observation from inference (interpretation) and know scientists’ explanations come partly from what they observe and partly from how they interpret their observations.
  • Measure and estimate the weight, length and volume of objects.
  • Formulate and justify predictions based on cause-and-effect relationships.
  • Conduct multiple trials to test a prediction and draw conclusions about the relationships between predictions and results.
  • Construct and interpret graphs from measurements.
  • Follow a set of written instructions for a scientific investigation.

Select a Lesson

Rainbow Shadows
Imagine you’re a painter.  What three colors do you need to make up any color in the universe?  (You should be thinking: red, yellow, and blue… and yes, you are right if you’re thinking that the real primary colors are cyan, magenta, and yellow, but some folks still prefer to think of the primary colors …
In a simplest sense, a kaleidoscope is a tube lined with mirrors. Whether you leave the end opened or tape on a bag of beads is up to you, but the main idea is to provide enough of an optical illusion to wow your friends. Did you know that by changing the shape and size …
Liquid Prism
In this experiment, water is our prism. A prism un-mixes light back into its original colors of red, green, and blue. You can make prisms out of glass, plastic, water, oil, or anything else you can think of that allows light to zip through. What’s a prism? Think  of a beam of light.  It zooms …
Sky in a Jar
Have you ever wondered why the sky is blue? Or why the sunset is red? Or what color our sunset would be if we had a blue giant instead of a white star? This lab will answer those questions by showing how light is scattered by the atmosphere. Particles in the atmosphere determine the color …
Light Tricks
When light rays strikes a surface, part of the beam passes through the surface and the rest reflects back, like a ball bouncing on the ground. Where it bounces depends on how you throw the ball. Have you ever looked into a pool of clear, still water and seen your own face? The surface of …
Black Light Treasure Hunt
Ever notice how BRIGHT your white t-shirt looks in direct sun? That’s because mom washed with fluorescent laundry soap (no kidding!). The soap manufacturers put in dyes that glow white under a UV light, which make your clothes appear whiter than they really are. Since light is a form of energy, in order for things …
Benham’s Disk
Charles Benhamho (1895) created a toy top painted with the pattern (images on next page). When you spin the disk, arcs of color (called “pattern induced flicker colors”) show up around the disk. And different people see different colors! We can’t really say why this happens, but there are a few interesting theories. Your eyeball …
In this lab, we are going to make an eyeball model using a balloon. This experiment should give you a better idea of how your eyes work. The way your brain actually sees things is still a mystery, but using the balloon we can get a good working model of how light gets to your …
Pinhole Camera
This is the simplest form of camera – no film, no batteries, and no moving parts that can break. The biggest problem with this camera is that the inlet hole is so tiny that it lets in such a small amount of light and makes a faint image. If you make the hole larger, you …
Ever play with a prism? When sunlight strikes the prism, it gets split into a rainbow of colors. Prisms un-mix the light into its different wavelengths (which you see as different colors). Diffraction gratings are tiny prisms stacked together. When light passes through a diffraction grating, it splits (diffracts) the light into several beams traveling …
Mixing Colors
There are three primary colors of light are red, green, and blue.  The three primary colors of paint are red, yellow, and blue (I know it’s actually cyan, yellow, and magenta, which we’ll get to in more detail later, but for now just stick with me and think of the primary colors of paint as red-yellow-blue …
Mixing Cold Light
Here’s a trick question – can you make the color “yellow” with only red, green, and blue as your color palette?  If you’re a scientist, it’s not a problem.  But if you’re an artist, you’re in trouble already. The key is that we would be mixing light, not paint.  Mixing the three primary colors of …
Disappearing Beaker
We’re going to bend light to make objects disappear. You’ll need two glass containers (one that fits inside the other), and the smaller one MUST be Pyrex. It’s okay if your Pyrex glass has markings on the side. Use cooking oil such as canola oil, olive oil, or others to see which makes yours truly …
Optics, Fire, and Eyes
If you’ve never done this experiment, you have to give it a try! This activity will show you the REAL reason that you should never look at the sun through anything that has lenses in it. Because this activity involves fire, make sure you do this on a flame-proof surface and not your dining room …
Microscopes and Telescopes
Hans Lippershey was the first to peek through his invention of the refractor telescope in 1608, followed closely by Galileo (although Galileo used his telescope for astronomy and Lippershey’s was used for military purposes).  Their telescopes used both convex and concave lenses. A few years later, Kepler swung into the field and added his own …
Light, Lasers, and Optics
When I was in grad school, I needed to use an optical bench to see invisible things. I was trying to ‘see’ the exhaust from a  new kind of F15 engine, because the aircraft acting the way it shouldn’t – when the pilot turned the controls 20o left, the plane only went 10o. My team …