Out of Darkness: An Introduction to Light Teacher s Guide

Transcription

1 Teacher s Guide Grade Level: 6-8 Curriculum Focus: Science Lesson Duration: Four class periods Program Description Out of Darkness: An Introduction to Light Light is a key element in our surroundings, enabling us to see, to perceive different colors, and to appreciate the beauty and diversity of our surroundings. In this informative program, students explore the basic characteristics of light, including reflection, refraction, luminosity, the spectrum, and the speed of light. They discover that light has energy and that plants produce their own food by using the energy of sunlight. The program also takes a look at how prisms and different types of lenses work. Simple experiments illustrating key principles encourage students to investigate the properties of light on their own. Discussion Questions What are direct sources of light? How does a radiometer show that light has energy? What do you call anything through which you can easily and clearly see? What are some examples of things that are transparent? What do you call something through which no light can pass? What are some examples of things that are opaque? What does it mean to describe something as luminous? What are some examples of things that are luminous? How do rays of light reflect off rough or smooth surfaces? Lesson Plan Student Objectives Explain that light is a source of energy. List basic characteristics of light. Contrast the sources, uses, and appearance of indoor and outdoor light. Differentiate between transparent and opaque materials. Demonstrate how light can be refracted and reflected. Demonstrate the action of a lens and differentiate between convex and concave lenses. Describe what happens when light passes through a prism and list the colors of the spectrum

2 Teacher s Guide 2 Create a light fact booklet. Make a pinhole camera. Materials Out of Darkness: An Introduction to Light video Computer with Internet access Prisms, a clear container, a small mirror, a flashlight (Procedures 6 and 9) Water glass, spoon, pencil or straw, vegetable oil (Procedures 7 and 8) Materials for making a pinhole camera or scope (Procedure 10) Procedures 1. Before students view the program, lead a general discussion about light. What is light? Why is light important? Define light as the form of radiant energy that can be seen by the naked eye. Explain that light that comes from a direct source such as the sun, a lightbulb, or the flame of a candle is called white light. Ask students these questions: Is white light really white? What happens when white light passes through a raindrop or a prism? Explain that white light is a mixture of every color of the rainbow. A prism or raindrop separates the colors. (Note: An actual demonstration with a prism will be useful.) What are these colors? Help students recall the colors in order with the name Roy G. Biv: red, orange, yellow, green, blue, indigo, violet. Tell students that they will be viewing a program about light. Ask them to watch for information on how light travels, what changes the way it travels, and how light and their eyes work together. 2. Light Facts After students view the program, ask them to brainstorm what they learned about light. Ask questions as necessary to prompt recall. Record responses on the board. Responses should include the following: Light comes from many sources. Light is a form of energy; it can do work. Plants use light to produce food and grow. Light travels in lines or rays. Light travels in a straight line unless it bumps into something. Light travels at 186,000 miles per second. It takes light from the sun over eight minutes to reach Earth. Light responds differently to different types of materials. Things that are luminous give off their own light. Reflected light reveals objects that are not luminous.

3 Teacher s Guide 3 How light reflects depends on the surface it hits. Light can bend (refract) when it goes from one kind of transparent material to another. Bands of color (called the spectrum) make up white light. 3. Light Facts Booklet Once students have compiled their list of light facts, have them copy and illustrate each one in booklet form. Illustrations can be simple sketches or a description of a demonstration contained in the video. 4. Light Indoors Review the concept that reflected light reveals objects that are not luminous. Ask students to think about the different kinds of electric lights in their home. Where are the lights placed? What are they used for? Where is the light that students use when they eat dinner? What kinds of light do students use for reading or doing homework? Do students use fluorescent lights? If so, where? How is the light that a fluorescent source gives off different from that of a regular, incandescent lightbulb? What could students use for light if a power outage caused their homes to lose electricity? Imagine the world without electric lights. How would daily life be different? 5. Light Outdoors Discuss seasonal changes of light the fact that at different times of the year the quality of the light we see around us is different. Review the seasons and the months each includes. What change occurs in the number of daylight hours as the seasons change? Ask students to describe the light in October, in July, currently, and at other times of the year. Why does the quality of light change throughout the year? (Help students understand that these changes are related to the position of the Earth in relation to the sun, the angle at which rays of sunlight are striking the Earth, as well as other factors like clouds.) 6. Review the concept of prisms and the spectrum. Why does light shining through a prism create a rainbow? What is the spectrum of colors that make up the rainbow? Are these colors always in the same order? Allow students time to experiment with sunlight or other light sources and a selection of prisms. Does every prism produce the same colors in the same order? Extension Activity Fill a clear container with water. Place a mirror inside the container on a slant, faceup. Ask students if they think this could act like a prism. If so, what will happen when light from a flashlight is directed into the water? Will a rainbow be produced? If so, can students predict where it will appear? Challenge Activity Ask students to find and make a list of household objects or materials that act like prisms and make rainbows. 7. Review the concept of lenses, how lenses work, and the difference between a concave and convex lens. Next have students make their own lens by pouring water into a clean glass, then holding a piece of paper with writing on it close to the glass. When they look at the writing through the glass, the writing will appear larger. Ask students to explain why this occurs. Help them understand that the curved glass acts as a convex lens, similar to the convex lens of a magnifying glass. 8. Refraction The program shows how a spoon in a glass of water appears to be broken because light bends as it travels from water into air. Students can extend this experiment by filling a glass half with water and half with vegetable oil. The water and oil will form separate layers. If students now place a pencil or straw in the glass, the item will appear to be broken in not one but two places. Ask students to explain why this occurs. (Oil has a different composition, or

4 Teacher s Guide 4 optical density, from that of water, and the angle of refraction is different. The angle at which rays of light bend when they go from one transparent substance to another depends on the composition of the substances.) 9. Reflection The following activity will help students better understand that light can reflect. Darken a room and place a mirror on the floor. Have students shine a flashlight on the mirror and observe how the beam bounces up and hits the ceiling. Next hit two chalky erasers together above the mirror. The dust will highlight the beam traveling from the light to the mirror and then to the ceiling. The chalk dust reflects the light. Extension Activity Have students experiment with changing the slant or angle of the beam from the light to the mirror. What happens to the slant or angle of the beam from the mirror to the ceiling? What relationship between the slant of the beams do students observe? (Help students see that the slant from mirror to ceiling is always the same as that from light to mirror.) 10. Pinhole Camera It is difficult for many students to understand that the eye s lens bends light rays so that they focus on the retina in such a way that the image is upside down. A pinhole camera can help them visualize this more clearly because it acts in much the same way as the human eye. Below are several Web sites that provide information on building a pinhole camera. If practical, allow students to work individually or in small groups to build their own cameras. Once cameras have been completed, discuss with students what they discovered about the eye, lenses, and sight by using their cameras. If photos have been taken, have these developed and displayed. The Pinhole Scope Making a Pinhole Camera (This one uses film and takes pictures.) How does a pinhole camera work? (information and additional links) Assessment Use the following three-point rubric to evaluate students work during this lesson. 3 points: Students were highly engaged in class discussions and class activities; produced a complete light facts booklet, including all of the requested information and illustrations; successfully constructed a working pinhole camera and demonstrated clear understanding of the principles involved. 2 points: Students participated in class discussions and class activities; produced an adequate light facts booklet, including most of the requested information and illustrations; constructed a satisfactory pinhole camera and demonstrated adequate understanding of the principles involved.

5 Teacher s Guide 5 Vocabulary 1 point: Students participated minimally in class discussions and class activities; created an incomplete light facts booklet with little or none of the requested information and illustrations; did not construct a satisfactory pinhole camera and demonstrated inadequate understanding of the principles involved. concave lens Definition: A lens that is thicker along the edges than in the middle Context: Rays of light that pass through a concave lens diverge or separate. convex lens Definition: A lens that is thicker in the middle than on the edges Context: Convex lenses bend rays of light so that they come together or converge at a focal point. lens Definition: A transparent piece of glass or plastic with a curved surface that bends light; a component of the eye which works in concert with the cornea to refracts light and focus it onto the retina Context: By changing the curvature of the eye s lens, one can focus the eye on objects at different distances from it. light Definition: Electromagnetic radiation that can be seen by the naked eye Context: Light enables us to see, to perceive different colors, and to appreciate the diversity and beauty of our environment. luminous Definition: Emitting self-generated light Context: Though the moon appears luminous, its light is actually reflected sunlight. opaque Definition: Impenetrable by light; neither transparent nor translucent Context: When light hits an opaque object, it bounces back. prism Definition: A piece of glass or other transparent material whose ends are equal and parallel triangles Context: Prisms refract white light into the colors of the spectrum. rays Definition: Thin lines of light

6 Teacher s Guide 6 Context: Rays of light pass easily through transparent materials such as air, glass, or water. reflection Definition: The bouncing of light off a surface that it strikes Context: A mirror image is produced by reflection of light off a smooth surface. refraction Definition: The bending of light, occurring when light travels from one transparent material to another Context: Refraction will cause a spoon that has been placed in a clear glass of water to appear bent or broken. shadow Definition: An unilluminated area Context: Shadows are created by the absence of light. spectrum Definition: As used in this program, the band of colors that make up white light Context: The colors of the spectrum are red, orange, yellow, green, blue, indigo, and violet. speed of light Definition: 186,000 miles per second through air or space Context: At the speed of light, it takes eight minutes for light from the sun to reach Earth. transparent Definition: Transmitting light; able to be seen through with clarity Context: Light can bend when it goes from one kind of transparent material to another. white light Definition: Light that comes from the sun or from an ordinary lightbulb Context: White light is a mixture of every color of the rainbow. Academic Standards National Academy of Sciences The National Academy of Sciences provides guidelines for teaching science in grades K 12 to promote scientific literacy. To view the standards, visit this Web site: This lesson plan addresses the following national standards: Physical Science: Properties and changes of properties in matter; Motions and forces; Transfer of energy

7 Teacher s Guide 7 Science as Inquiry: Abilities necessary to do scientific inquiry; Understandings about scientific inquiry Mid-continent Research for Education and Learning (McREL) McREL s Content Knowledge: A Compendium of Standards and Benchmarks for K 12 Education addresses 14 content areas. To view the standards and benchmarks, visit This lesson plan addresses the following national standards: Science Physical Sciences: Understands the sources and properties of energy; Understands forces and motion Science Nature of Science: Understands the nature of scientific inquiry Life Skills Thinking and Reasoning: Understands and applies basic principles of logic and reasoning; Effectively uses mental processes that are based on identifying similarities and differences; Understands and applies basic principles of hypothesis testing and scientific inquiry Language Arts Viewing: Uses viewing skills and strategies to understand and interpret visual media Support Materials Develop custom worksheets, educational puzzles, online quizzes, and more with the free teaching tools offered on the DiscoverySchool.com Web site. Create and print support materials, or save them to a Custom Classroom account for future use. To learn more, visit Credit Patricia A. Peirson, freelance writer; former elementary school and adult ESL educator