The Science of Color

Using affordable supplies, demonstrate how light is reflected or absorbed when passed through color filters.

• If you’re short on materials, projecting using a document camera can help students see the effect.
• For students with colorblindness, consider adding a legend to your colored beads using numbers (i.e., red = 1, blue = 2, etc.) and adding these numbers to your images so that all students can follow along. This can be easily accomplished by writing the numbers and legend on a white piece of paper and putting the container of beads on top.
• For younger students, it may be helpful to display a picture or screenshot of the beads without a filter to help them compare and follow along. Instruct them to pick a bead to focus on as you change the filter to help them see the changes.

• If teaching online, the beads can be placed on a string and worn as a bracelet for ease of displaying on a computer camera. You can also cut out squares or stars from colored construction paper and attach them to a piece of white paper.

In astronomy, we look at stars and distant galaxies, studying the light that reaches our telescopes on the ground and in space. The color of the light we see tells us a lot about what we’re looking at, how far away it is, and even how fast it’s moving! Scientists and engineers at NASA can use space-based telescopes to observe and collect wavelengths of light that communicate different information about the universe, but these can be expensive to launch and difficult to maintain. When possible, it may be desirable to use balloons to carry a telescope into the stratosphere. These balloon missions, such as NASA Jet Propulsion Laboratory’s ASTHROS, provide a balance between the space-based and ground-based telescopes you may be more familiar with.

ASTHROS will lift off from Antarctica and fly to 130,000 feet (40,000 m) where it will be less impacted by the interference of light pollution and water in the atmosphere. It will draw upon well-studied weather patterns as it climbs and will collect far-infrared light with an 8.4 foot (2.5 m) telescope.

Much like telescopes in space or the one in your own backyard, ASTHROS uses filters – materials that allow different types of colors to pass through them – to better study specific parts of the light that is detected.

When we look at an object in normal light, we’re really looking at how it reflects or absorbs white light. For example, we think of plants as green because they absorb red light and bounce the green light back to our eyes. When we use a filter, we allow only certain wavelengths of light to reflect back to our eye. Depending on the filter, this can make objects appear lighter or darker and can even reveal objects that are undetectable in other wavelengths.

• Consider your student artists, who may have seen this effect when mixing paint. Pigments in paint or ink balance what light is absorbed and what light is reflected to result in the colors we see. By mixing different colors of paint or ink, we get entirely new colors.
• We can also view undesirable filters as something called interference. Ask students why we may want to launch in Antarctica (as opposed to near large cities) or above the air and water that make up our atmosphere. How might these conditions contaminate or filter out the data we’re looking for?
• Depending on the grade level, consider mentioning that while we’re demonstrating larger patterns in color, astronomers may look for very specific wavelengths of light instead of larger bands of color, like blue or red. This is because every element in the periodic table has a unique pattern of wavelengths of light. So with a very sensitive instrument – one better than our eyes – you can even see exactly what chemicals make up distant galaxies!
• Remind students that the colors we see are in the visible spectrum, a tiny sliver of the electromagnetic spectrum. Filters also work on portions of the electromagnetic spectrum that we can't see, such as in infrared and ultraviolet. See extension below.

To really impress your students, extend the demonstration using a standard TV remote control and the front facing camera of your phone or the camera on your computer.

1. If demonstrating in class, have your students confirm that when looking at the bulb of a remote control with their naked eye, they don’t see any light when pushing the buttons.If teaching remotely, this can be accomplished simply by asking students if they normally see any light beam when they use their remote controls.
2. Now point the remote control at your computer camera or front facing phone camera and press any button. You should see the light bulb illuminate as it passes through your camera’s filter. Be sure to let your students try this at home!

Note: This is best performed on a phone's front-facing camera or older phone cameras. Newer phones have more selective color filters that no longer transmit infrared light.