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Electromagnetic Spectrum

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Electromagnetic Spectrum National Aeronautics and Space Administration The Electromagnetic Spectrum The light we can see with our eyes represents only a very small portion of the continuous range of electromagnetic waves that form the electro- magnetic spectrum. On one end of the spectrum are radio waves, with wavelengths that can be as large as mountains. On the other end of the spectrum are gamma rays, with wavelengths as small as atomic nuclei. Frequency is a measure of the number of wave crests passing by a given point per second (or hertz). Shorter wavelengths have higher frequencies and higher energies than longer wavelengths. Although our eyes can see only visible light, astronomers use all regions of the electromagnetic spectrum to study the universe. Each type of electromagnetic energy provides different clues about the properties of celestial objects. Scientists build devices that can detect different regions of the electromagnetic spectrum. Computer image-processing techniques then code the light into pictures that we can see. Image:Image: TheThe WhirlpoolWhirlpool GalaxyGalaxy inin visiblevisible light,light, asas seenseen byby thethe HubbleHubble SpaceSpace Telescope.Telescope. Frequency: 5 7 9 11 13 15 17 19 21 (in hertz) 10 10 10 10 10 10 10 10 10 Lower frequencies Higher frequencies RadioRadio MicrowaveMicrowave InfraredInfrared UltravioletUltraviolet X-RayX-Ray GammaGamma RayRay Longer wavelengths Shorter wavelengths Wavelength: 10 4 10 2 1 10-2 10-4 10-6 10-8 10-10 10-12 10-14 (in meters) VisibleVisible 1 wavelength Wavelength is the size of: Mountains Buildings Humans Houseflies Pinpoints Bacteria Molecules Atoms Atomic Nuclei The Whirlpool Galaxy at different wavelengths Scientists use a variety of telescopes in space and on the ground to measure the full range of electromagnetic waves emitted by celestial objects. Radio Infrared Visible Ultraviolet X-Ray The Classroom Activities To use an overhead projector, place two pieces of 8-inch spectrum appears to have boundaries. Asking if black plastic, 12" x 12", 2-4 mil thick Electromagnetic This poster contains three classroom activities The Visible Invisible Light Safety Issues by 10-inch dark paper on the projector to create a “slit” there is anything beyond the red and violet ends of clear plastic baggie, 1 gallon size designed to introduce middle and high school about 2.5 centimeters (1 inch) wide on the base plate the spectrum introduces the notion of “non-visible” students (grades 6–12) to different portions of the Spectrum Sources and wax paper, 12" X 12" We advise against incandescent black light bulbs. of the projector. Turn on the projector lamp and focus electromagnetic energy. Human skin is sensitive Spectrum electromagnetic spectrum, including those used If that type of bulb is the only one available, be Target Grade Levels: 6–12 the “slit” on a white wall or screen. Place the diffraction to the ultraviolet energy beyond the violet light; Detectors by Origins missions. Suggested science standards, For the stations: aware that they can become very hot, so caution grating (about 4 or 5 inches square) in front of the upper it sunburns. And, skin senses the infrared energy Overview vocabulary, and science background information are Target Grade Levels: 6–12 students not to touch the bulb. And although provided to facilitate lesson planning. The activities Purpose lens (head) of the overhead, and rotate the grating until beyond the red light as heat. Demonstration Station normal fluorescent black lights are considered the spectrum appears on either side of the projected slit can be done separately or together. To introduce the electromagnetic spectrum. Visible Light completely safe, please advise students not to The light that we see with our eyes – visible In astronomy, scientists use the properties on the wall or screen. 2. How Do Color Filters Work? Purpose Understanding electromagnetic energy often begins SOURCE: flashlight (with batteries) stare directly into the fluorescent bulbs for light – represents only a small portion of the of light to learn about celestial objects that The Visible Spectrum provides instructions DETECTOR: plain white paper 8 1/2" X 11" with studying the visible spectrum. Visible light Transparent, colored objects transmit only a At classroom stations, students gain direct experi- extended periods or from close range. Shorter electromagnetic spectrum. Developing the tech- are too far away to visit. Each portion of the for creating a visible spectrum with an overhead To use a slide projector, create a 35-millimeter slide that is accessible and emphasized in most textbooks. portion of the visible spectrum. Place common ence with different sources of electromagnetic energy Radio (FM) wavelength black lights used in mineral explora- nology to detect and use other portions of the electromagnetic spectrum provides unique projector. Introduce the electromagnetic spectrum has a clear “slit” about 0.5 centimeters (1/4 inch) wide by Students bring personal observations of the transparent objects like sunglasses, colored report — most of which is not visible to the human eye. SOURCE: radio station tion or to sterilize surfaces should NOT be used. electromagnetic spectrum – the “invisible” light clues about the nature of our universe. The by showing students that white light is composed using unexposed film, or black electrical tape in a slide DETECTOR: small battery-operated FM radio. spectrum from the natural world: rainbows; prisms; covers and plastic wrappers on the “slit” of the Each station will have a source of electromagnetic They can be dangerous to eyes and skin and can that our eyes cannot see – has had a tremendous missions and research programs in NASA’s of a rainbow of colors. Students can draw the mount. Turn on the projector and focus the “slit” on the Aluminum foil (enough to completely cover diffraction grating glasses; and other commercial overhead projector (or into the beam from the slide energy, possible “detectors,” and sheets of material burn them much like a severe sunburn. impact on our daily lives. When you listen to a Astronomical Search for Origins program visible spectrum and explore how common objects wall or screen. The diffraction grating is placed in front the radio, its antenna, and any headphones). items decorated with refractive materials (pencils, projector) to discover how they “filter” light. The to test as potential “transmitters” or “shields” for radio, heat your food in a microwave oven, use a use innovative technologies to observe the “filter” light. Use these activities to engage students’ of the lens. Again, rotate to produce the spectrum on [For large classes, set up two of each of the numbered signs, etc.). Begin with these observations to engage filters used for theatrical lighting are designed to the electromagnetic energy. Detecting and blocking remote control, or have an X-ray taken, you are universe at a variety of wavelengths (ultra- interest in electromagnetic energy. students' curiosity about light and, more broadly, the wall. stations.] selectively transmit color, and offer a more dramatic (“shielding”) various forms of electromagnetic Procedure using “invisible” light. violet, visible, and infrared) in search of the electromagnetic energy. Station 1 demonstration of how light is filtered. Viewing energy helps students realize there are forms of answers to two enduring human questions: The Herschel Infrared Experiment With either type of projector, the spectrum will appear on Infrared Light objects in different regions of the electromagnetic electromag-netic energy that we cannot see. Demonstration – Defining Sources, helps students to expand their knowledge of the Materials both sides of the “slit” You can move the projector to place SOURCE: infrared light (heat lamp) Where did we come from? spectrum through the use of filters and different DETECTOR: student’s hand Detectors, Transmitters, and Shields electromagnetic spectrum. Students will discover the spectrum at the best place for students to observe. Note: X-rays and gamma rays are not included as Overhead projector; diffraction grating*; kinds of telescopes gives astronomers more informa- Are we alone? the “invisible” light that lies just beyond the red Note that this works best in a darkened room. part of this classroom activity for several reasons, Station 2 1. Sources. Shine the flashlight from the demon- and two pieces of 8" X 10" dark paper. tion about the universe. end of the visible spectrum – infrared light. Use most importantly because they are harmful if not Infrared Light stration station at students. Say, “This flashlight is a OR this as an outdoor class laboratory activity, a Activities used properly. SOURCE: VCR/TV remote control source of light.” Ask, “What are some other sources Slide projector; diffraction grating*; one 35-mil- *Note on Diffraction Gratings and Prisms: student learning station, a demonstration, or as DETECTOR: TV monitor or other device triggered of light energy that we can see?” Explain that while Vocabulary limeter slide mount; and unexposed film or black 1. The Colors of the Visible Spectrum Diffraction gratings produce a bright, broad visible by remote part of a science fair project. Materials most objects reflect light, they are not considered to electrical tape. spectrum that students find easier to observe. Electromagnetic energy: A form of energy that travels through space as vibrations of electric and Students use color pencils or crayons to draw and label Holographic gratings perform best. A prism placed Station 3 be the source of that light. Sources of light generate Invisible Light Sources and Detectors Color pencils or crayons; common transparent For the class: Ultraviolet Light the spectrum. They may record more or fewer colors in a light beam of a slide projector will also produce and emit the light themselves. magnetic fields; also called radiation or light. gives students direct experience with radio, infrared, objects like sunglasses; colored report covers; and SOURCE: black light — fluorescent than the classic “ROY G BIV” (red, orange, yellow, a visible spectrum, but it will likely be fainter, with Activity worksheets for each student visible, and ultraviolet waves.
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