Lesson: The Energy of LightContributed by: Integrated Teaching and Learning Program, College of Engineering, University of Colorado at Boulder
Educational Standards :
Learning Objectives (Return to Contents)
After this lesson, students should be able to:
Introduction/Motivation (Return to Contents)
What is light? Can you give an example of light? (Possible answers: Light bulb, flashlight, the sun.) From where does light come? Light is a form of energy. Items such as light bulbs and television screens give off this light energy. Our eyes change visible light energy waves into something we can see. Visible light energy is just one form of light energy. There are invisible forms of light energy, or light energy we cannot see, such as infrared, ultraviolet, radio and x-ray light energy. All light energy is generated by light waves.
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 spectrum and all of the possible angles shown by the slinky.
Color is a product of visible light energy. Different colors represent light waves vibrating at different speeds (frequencies). Do you know that most colors of light can be made by mixing together just three colors — red, blue and green?
Light has other properties that make it fun to learn about. Light waves can bounce off an object; this is called reflection. You can see this when you look at your reflection in a mirror or you see the sky and clouds reflected in a pool of water. The light bounces off the shiny surface (mirror glass or water) back at us. Light waves can also refract; this happens when the light waves are bent as they pass through a clear object. The lens in a pair of eye glasses helps people see more clearly by bending the light rays to help the person's eye adjust images for a distance close up or far away.
Different length light waves are all reflected in the same way, but not refracted the same. Red light waves bend the least and violet light waves bend the most, which gives us a rainbow effect when light bounces off prisms, glass and raindrops.
The brightness of any light source is determined by the amount of light energy it contains. Do you know that a laser light is even brighter than sunlight? It has so much concentrated energy that it can burn through metal. Engineers use lasers in hundreds of ways — in industry, medicine and surgery, to make holograms, read bar codes and compact disks, and send messages along fiber-optic cables.
The sun and other stars emit radio waves, sending them through space. To detect them on Earth, aerospace engineers use radio telescopes. These huge disks face the sky to collect and focus wave energy. The largest single-dish radio telescope is at Arecibo, Puerto Rico. The dish is built into karst topography — a natural hollow in the ground — and is 1,000 feet across. As the Earth moves, the disk turns to point at different parts of the sky.
Light energy is used by engineers in many other ways as well. Engineers have learned to control light using things like prisms and magnifying lenses. Engineers use light for developing medical equipment, x-ray machines, telescopes, cameras, computers and microscopes. Engineers need to know how light energy works to be able to create these cool products and equipment that help people every day. Today we are going to learn more about light energy and where it is found all around us.
Lesson Background & Concepts for Teachers (Return to Contents)
Light is a type of energy formed by a combination of electrical and magnetic rays, known as electromagnetic (EM) waves. (For a good, basic description and graphics on the electromagnetic spectrum, see NASA's Imagine the Universe website at http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html.) Use the attached Electromagnetic Spectrum for a classroom visual aid; it is suitable for making overhead projector transparencies or student handouts.
Visible light is only one type of EM wave. We use different kinds of electromagnetic waves for many different purposes. Radio transmitters, for example, generate artificial radio waves that carry radio and television programs in coded form by varying the height of the waves.
We see light. We use light every day, in endless ways. Light is a type of energy created by a combination of electrical and magnetic fields. In some ways, light travels as waves giving it typical wave features. For example, the color of light depends on the length of the wavelength of the beam of light. However, in other ways, light seems to be a stream of tiny particles or packets of energy called photons. Scientists have come to accept both of these ways of understanding light. They call the combination of these two properties the "wave-particle duality" of light. Nothing travels faster than light, which travels at a speed of 186,000 miles (299,792 kilometers) per second.
Vocabulary/Definitions (Return to Contents)
Associated Activities (Return to Contents)
Lesson Closure (Return to Contents)
Today we learned about light energy. Light energy travels in waves. What are the types of light energy? (Answer: Visible, infrared, ultraviolet, x-ray and radio.) What type of light energy do colors fall into? (Answer: Visible light energy.) What are some properties of light energy? (Answer: Reflection, refraction, waves, photons, wavelengths.) What is reflection? (Answer: When light bounces off the surface of an object.) What is refraction? (Answer: When light bends as it passes through a material.) Engineers use light to create many things that benefit our society. What are some objects that engineers use to control light energy? (Possible answers: Eye glasses, microscopes, medical equipment, magnifying glasses, prisms, polarized sunglasses.) When you go home tonight, tell a friend or family member what you learned about light energy and point out something around you that an engineer has designed that uses light energy, such as a lamp, camera lens, reading glasses, television or computer.
Attachments (Return to Contents)
Assessment (Return to Contents)
Know / Want to Know / Learn (KWL) Chart: Before the lesson, ask students to write down in the top left corner of a piece of paper (or as a group on the board) under the title, Know, all the things they know about light energy. Next, in the top right corner under the title, Want to Know, ask students to write down anything they want to know about light energy. After the lesson, ask students to list in the bottom half of the page under the title, Learned, all of the things that they have learned about light energy.
Discussion: As a class, review and discuss students' understanding of light energy. Ask the students:
Lesson Summary Assessment
Roundtable: Have the class form into teams of 3-5 students each. Ask the class a question with several possible answers: How does an engineer use light energy? Have the students on each team make a list of answers by taking turns writing down ideas on a piece of paper. Students pass the list around the group until all ideas are exhausted. Have teams read aloud the answers and/or write them on the board.
KWL Chart (Conclusion): After the lesson, ask students to list in the bottom half of the page under the title, Learned (or on the board), all of the things that they have learned about light energy.
Class Definitions: To reinforce knowledge, have students develop their own definitions for refraction, reflection, visible light and wavelength. Do this in a class discussion or in teams in which the students develop a definition (written and/or illustrated) and read it aloud to the rest of the class. Post the class definitions in the classroom or on the board.
Lesson Extension Activities (Return to Contents)
For an excellent demonstration showing the refraction and reflection of light, shine a multimedia laser pointer into a fishbowl. Fill the fishbowl with water, place a mirror in the bottom, turn off the lights and shine a laser pointer into the water.
References (Return to Contents)
Dictionary.com. Lexico Publishing Group, LLC. Accessed September 22, 2005. (Source of some vocabulary definitions, with some adaptation.) http://www.dictionary.com/
Electromagnetic Spectrum. Updated 1997-2005. NASA's Imagine the Universe, Goddard Space Flight Center. Accessed September 22, 2005. (Good basic description and graphics) http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html
Graham, I., Taylor, B, Farndon, J. and Oxlade, C. Science Encyclopedia. 1999, p. 78-90.
Irving, Bruce. Optics for Kids: Science and Engineering. Optical Research Associates, Pasadena, CA. Accessed September 28, 2005. (Excellent resource with graphics) http://www.opticalres.com/kidoptx.html
ContributorsSharon D. Perez-Suarez, Jeff Lyng, Malinda Schaefer Zarske, Denise Carlson
Copyright© 2005 by Regents of the University of Colorado
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. 0226322. 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.
Supporting Program (Return to Contents)Integrated Teaching and Learning Program, College of Engineering, University of Colorado at Boulder
Last Modified: March 11, 2014