Hands-on Activity: Stations of Light
Educational Standards :
Learning Objectives (Return to Contents)
After this activity, students should be able to:
Materials List (Return to Contents)
The materials at each station are re-usable for an unlimited number of teams. The total cost for four stations is ~$20.
Station 1: Bending Light
Station 2: Lens and Light
Station 3: Prism Rainbows
Station 4: Polarized Light
Introduction/Motivation (Return to Contents)
Light is amazing! It is a form of energy that can bend and bounce, and it comes in all different colors. What do you call it when light bounces off something? It is called reflection. And, that is what is happening when we look at our reflection in the mirror — light is bouncing back at us from the mirror. When light bends through something, such as water, it is called refraction. Have you ever been in a swimming pool and seen someone in the water look cut off at the surface of the water? What you are seeing is due to refraction. Have you ever played with a prism? Well, we are going to look at one today to see another form of bending, or refraction, of light. How about a magnifying glass? Well, that is a way light energy waves are refracted to make an image seem larger.
Demonstration idea: If a slinky is available, use it to show how waves vibrate in different wavelengths. Explain how the different "wavelengths" correspond to different colors. Use the slinky to show the class that waves can vibrate in any plane (vertical, horizontal or any angle in between). White light contains all of the wavelengths of the visible light spectrum (see Figure 1) and all of the possible angles shown by the slinky.
Who remembers the colors of the rainbow? Have you ever noticed that the colors of a rainbow are always in exactly the same order? Show students the Visible Light Spectrum visual aid (the same as Figure 1). Inform them that ROY G BIV is a good way (acronym) to remember the order of the colors of the rainbow. In addition to these visible light waves, there are many more waves of light that cannot be seen with the human eye! Show students the Electromagnetic Spectrum visual aid. Ultraviolet (UV) waves are even shorter than violet waves and infrared waves are longer than red waves. We can only see the colors in the middle, the visible light spectrum.
Do you know which of these light energy waves causes sunburn and can hurt our eyes. (Answer: Ultraviolet light waves.) What do we do to protect ourselves from UV rays? (We wear hats, sunglasses and sunscreen.)
How does light energy affect us? Our eyes are sensitive to the brilliance of sunshine. Ultraviolet light penetrates clouds and fog, and is reflected back at us from snow and water. If unprotected from the ultraviolet waves, our eyes can be burned and/or permanently damaged. We can reduce this risk by wearing a high-quality pair of polarized sunglasses designed by engineers to limit the amount of ultraviolet light reaching our eyes.
How do polarized sunglasses work? Well, if we have a piece of paper containing a vertical (up and down) slit, what light do you think would pass through? Only waves in the vertical plane would pass through. The same applies for a horizontal slit and horizontal waves. When light reflects off water, all of the waves are oriented horizontally. This causes the intense glare off the water's surface you may have noticed. Polarized sunglasses work much like a letter going in to a mail box slot. If the letter is not positioned correctly then it cannot go into the mail box.
What do you predict would happen to light trying to pass through two polarized lenses oriented perpendicular to each other? (Answer: Wait for the hands-on activity to find out for yourself!)
Years ago (even in prehistoric times), Inuit people (also called Eskimos) who live in the snowy Arctic carved goggles of wood or bone with a narrow horizontal slit across the front. This allowed them to better see in "white out" snow conditions when light was coming from every direction and all contours were missing. How do you think this worked? How is this similar or dissimilar to the polarized sunglasses? (Answers: This is the same way that polarized sunglasses work. The horizontal slits only allowed part of the light waves, the horizontal ones, through to the Inuit's eyes.)
In addition to designing sunglasses that protect your eyes, engineers apply their knowledge of polarized light in laser applications, electron microscope imaging and medical imaging techniques.
Today, you will work in small teams and rotate through four stations where you will examine light energy behavior in more detail: refraction, magnification, prisms and polarization.
Vocabulary/Definitions (Return to Contents)
Procedure (Return to Contents)
Before the Activity
With the Students
Station 1: Bending Light
What's happening? The ruler appears to be bent at the surface between the water and the air. As the ruler approaches horizontal, the bend appears to increase. This is because when light travels across the border of two transparent media (such as air, glass, Lucite, etc.), the path of light bends. This phenomenon is called refraction.
Engineering connection: Lighting engineers are interested in the properties of light, especially natural daylight. Energy engineers study light properties to determine the best type of windows to put in a building. They are concerned with how much visible light can pass through the window and where it will land in the space, as well as how much illumination and energy the light adds to the space. Glass with high visible transmittance allows much light into the space; glass with high solar heat gain coefficients allows much energy to enter the space.
Station 2: Lens and Light
What's happening? Some students may notice that images flip when you hold the magnifying glass at a certain distance. This is because the image converges at a focal point. When the image diverges beyond this point, its orientation is flipped (see Figure 2).
Engineering connection: Engineers use their knowledge of light energy and lenses as they design prescription eye glasses, reading glasses, cameras, contact lenses, eye surgery equipment and techniques, solar energy collection equipment, telescopes, microscopes, satellites, optics and lasers. Using a lens as a light-collecting tool enables engineers and scientists to take photographs in dark rooms and invent other devices to improve our vision of the very tiny, very far away, and locations unsuitable for human life (in hot volcanoes, deep the ocean, in outer space).
Station 3: Prism Rainbows
What's happening? The shorter the wavelength, the more that light is bent or refracted by the prism. In a similar situation, light passing through water (or water droplets in the air) can create a rainbow.
Engineering connection: Prisms are used in all sorts of engineered devices. Binoculars use pairs of prisms to lengthen the path of light so that far-away objects appear closer, and also to turn the image, which is reflected off a mirror upside down. Prisms are also used to focus light rays in medical equipment and general lighting applications.
Station 4: Polarized Light
What's happening? Light particles travel in waves. Every light wavelength in the visible spectrum corresponds to a specific color (see Figure 1). White light contains all the visible wavelengths. A polarizing filter consists of many parallel tiny openings. Light waves traveling in the same plane as the openings pass through the filter, while all other waves of light are blocked (see Figure 5). Light that has passed through the filter is considered "polarized" — its light waves travel in approximately parallel planes. The sunglasses' lenses and the plastic film are both polarizing filters. When the plastic film is rotated to only allow light traveling in a horizontal plane to pass through, fewer and fewer light waves can pass. When the two filters are oriented perpendicular to each other, no light can pass. When the polarized lenses and the polarized film are oriented at 90 degrees, the lenses become opaque.
Engineering connection: Engineers apply their knowledge of polarized light in laser applications, electron microscope imaging and medical imaging techniques. They also create sunglasses and camera filters that reduce the glare/reflections from the sun. Polarized light is also used to determine how forces impact machine parts. A copy of the part is made in plastic and viewed under a polarized light as a force is applied. Color bands appear where force is being transferred through the object.
Conclude the activity by bringing the class together for a discussion and review of their worksheet observations. Review the "What's happening?" and "Engineering connection" information provided in the Procedure section. Conduct the post-activity assessment activities as described in the Assessment section.
Attachments (Return to Contents)
Troubleshooting Tips (Return to Contents)
These stations could also be conducted as class demonstrations.
If students are not familiar with the visible electromagnetic spectrum, show them the attached Visible Light Spectrum so they can note the order of colors refracted through the prism (ROYGBIV).
Assessment (Return to Contents)
Slinky Demo and Discussion: Use a slinky to show the class how waves can vibrate in any plane and in different wavelengths. White light contains all the wavelengths of the visible spectrum and all the possible angles shown by the slinky. Have the students recall the colors of the rainbow and use the slinky to demonstrate that short waves represent violet light and long waves represent red light. Ask the students the following discussion questions:
Activity Embedded Assessment
Worksheet: Have the students record their observations on the Light Energy Worksheet. Review their answers to gauge their mastery of the subject.
Worksheet Discussion: Discuss with students what is occurring. Have them share their results with the class. For example, have the students discuss why they think the beam of light bent more under water. Also discuss in which type of media refraction occurs. (Answers: Water, air, glass, clear plastic, etc.)
Colors of the Rainbow: Have students make a list of colorful objects, or collect colorful objects from around the classroom. Then have them re-order the objects by wavelength, following the colors of the visible light spectrum or rainbow, with red as the longest wavelength and violet as the shortest.
Make It Real: Engineers use light everywhere! Ask students to provide examples of where and how light energy is used. Generate a class list. Can they think of at least one use that involves a mirror, a lens, a prism and a polarized lens? (Possible examples: To see using flashlights and lamps; reflected light using mirrors and in cameras; visible light in light shows, neon signs and computer screens; for medical technology in x-rays and medical imaging equipment.)
Activity Extensions (Return to Contents)
The Inuit (also called Eskimos) of the Arctic invented sun goggles by cutting slits out of bone, wood or ivory. These native peoples used natural materials to prevent snow blindness and protect their eyes from the glaring bright light reflecting from water, snow and ice. Have students make their own arctic sunglasses. Follow instructions at NASA's Snow Goggles and Limiting Sunlight website,http://solarsystem.nasa.gov/educ/docs/Snow_Goggles.pdf.
Have the students evaluate the difference between convex and concave lenses. These lenses have different types of focal points, and the images in the lenses look different.
Have the students research the optics of the Hubble Space Telescope. This huge lens orbits about 600 km (375 miles) above the surface of the Earth. It completes one orbit around the Earth every 97 minutes. The Hubble weighs about 11,000 kg (24,000 lbs) on Earth. It is 13.2 meters (43.5 ft) long with a maximum diameter of 4.2 meters (14 ft). As with most telescopes, it is its light collecting power that makes it so effective. It has two mirrors, one is 2 meters (7 ft) wide. Start your research at the NASA (National Aeronautics and Space Administration) website.
Have the students conduct a library or Internet search to learn more about wavelengths. What wavelengths are longer and shorter than the visible spectrum wavelengths? For example, longer than the red wavelengths are invisible infrared (~750 nanometers to 1 millimeter in wavelength), microwaves (1 millimeter to 1 meter in wavelength) and short-wave radio (10-20 meters in wavelength) wavelengths. Provide examples of how engineers have used their understanding of the properties of these invisible wavelengths to create equipment and instruments useful in our everyday lives.
Activity Scaling (Return to Contents)
References (Return to Contents)
The Electromagnetic Spectrum. Updated August 8, 2003. IMAGERS (Interactive Multimedia Adventures for Grade School Education Using Remote Sensing), GSFC Laboratory for Terrestrial Physics, National Aeronautics and Space Administration (NASA).
ContributorsSharon D. Perez-Suarez, Jeff Lyng, Malinda Schaefer Zarske, Denise Carlson
Copyright© 2005 by Regents of the University of Colorado.
Supporting Program (Return to Contents)Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Acknowledgements (Return to Contents)
The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.