The ElectroMagnetic Spectrum:
more than just the rainbow
An exhibit at the Natural Science Center of Greensboro
built by the 2007-8 Senior Integrated Science class at
Greensboro Day School,
funded by the Toyota TAPESTRY program
Exhibit Description
This exhibit describes all six parts of the Electromagnetic Spectrum (gamma rays, x-rays, ultraviolet, visible, infrared, and radio). For each portion of the spectrum, the exhibit explains its basic properties and a brief history of its discovery, and the usage astronomers make of that part of the spectrum is discussed as well. Here is a photo showing the finished exhibit.
(For other photos, see below.) The exhibit is located in the “Astronomy Hall” of the Natural Science Center of Greensboro, just outside the entrance to the Omnisphere/planetarium, where audiences gather to await entrance to the theatre prior to the various shows. This prominent placement, not to mention the “cool” factor of the thermal infrared images being displayed, ensures that a high fraction of NSC visitors will interact with this exhibit. In observing NSC visitors since we installed the exhibit, the vast majority passing through that hallway stop to interact with it.
The exhibit incorporates videos of students explaining various aspects of different parts of the electromagnetic spectrum. Each video segment is incorporated into a PowerPoint slide containing other text and graphics, displayed on a 32-inch monitor. Which PowerPoint slides are displayed is controlled by the visitor, by passing a hand over one of six sections of a graphic bar representing the entire EM spectrum. Capacitive touch sensor circuits within the bar detect the user’s choice, signaling a Parallax BS2 microcontroller, which then commands PowerPoint, via an RS232 serial connection, to display the relevant slides and videos. In the absence of user input, the exhibit automatically advances through all parts of the spectrum.
In addition to the 32-inch monitor, two 19-inch monitors display visible-light and thermal-infrared images of the exhibit and visitors produced by two cameras placed on a small shelf located on the wall opposite the display case. A large vinyl banner, carrying a title, instructions, and images of the Milky Way galaxy in various parts of the EM spectrum lines the back of the display case.
Most parts of the spectrum have an associated demonstration. They are...
RADIO A boombox tuned to an AM frequency with no local stations is located in front of the 32-inch monitor. A wire protrudes from the right side of the spectrum bar, near the RADIO label, and is next to a flattened fork that is bolted in place. When the wire, which is connected to a low-voltage power source, is strummed across the tines of the fork, radio waves are transmitted and can be heard via the boombox.
INFRARED A Fluke Insight XST thermal-infrared camera is mounted on the wall opposite the display case. A monitor within the case displays the IR image of the exhibit and people standing in front of it. A Peltier solid-state cooler/heater is mounted on the IR portion of the spectrum bar; it cyclically turns dark and bright as it cools and heats, respectively, under the control of the BS2 microcontroller. A thick book is available in a wall-mounted holder, to the right of the spectrum bar. Visitors can place their hand on the cover of the book and then, after a few seconds, open the book, turn the pages and see how far into the book the heat of their hand had reached. These and other experiements the visitor can perform are described in a sign located to the right of the infrared image display monitor.
VISIBLE A convex lens projects an image of a compact fluorescent lightbulb (both are to the left of the large monitor) onto a white screen (located to the right of the large monitor.)
ULTRAVIOLET A large black box contains two so-called "blacklights" emitting UV. Next to these lights is a small selection of rock samples containing fluorescent minerals that glow under UV. Also in the box is a petrie dish of powder laundry detergent containing "brighteners" -- fluoresence chemicals that make clothing appear to be cleaner than it really is.
X-RAY A large LED light panel backlights several x-ray shadow images of various objects (scissors, paperclip, book, etc) and a human hand.
GAMMA RAY no demonstration
Photos of the exhibit and its construction can be found on the 2007-8 SIS photos page. Scroll down the page, and click on any thumbnail image to see a full-size version.
Powerpoint and Video Files A laptop computer runs the PowerPoint presentation with embedded video clips. Because of the videos and the extensive usage of animation, it cannot run within a web browser. If you would like to see the presentation, download this zip archive (31 MB) and uncompress. Then start the presentation "ems.ppt" within the folder. Video files are WMV format.
BS2 code The exhibit is controlled by a Parallax BS2 microcontroller running the following custom PBASIC code. If you have the Stamp Editor software, here is the code in BS2 format.
Graphics The museum visitor can control which PowerPoint slides and videos are displayed by passing a hand over whatever portion of the electromagnetic spectrum they want to learn more about, on a 4-foot-wide, 8-inch-high representation of the spectrum mounted on the front edge of the displaycase. The graphic is printed on durable, 0.25-inch plastic mounted on a hollow triangular prism structure built of plywood. The interior of the spectrum bar contains the six capacitive touch-sensor circuits, BS2 miscrocontroller, amplified speakers for playing the audio narration, and three solid-state relays under control of the BS2 (which in turn control the blacklights, Peltier cooler/heater, and boombox.)
The backdrop of the display case has a 7-foot-wide, 4-foot-tall vinyl banner carrying a title, introduction, and instructions, plus a series of images of our galaxy, the Milky Way, taken using different parts of the electromagnetic spectrum.
Click on the thumbnail graphics below to view or download the full-size versions.
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spectrum bar
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display case backdrop |
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Circuit Schematics The capacitive touch-sensor circuits used in this exhibit are centered on the Quantum Research Group, Ltd, QT113 chip. If you are interested, view the circuit schematic and datasheets. A total of six such circuits are used, one behind each section of the spectum bar. Each uses a 24 inch² piece of sheet metal as the sensing antenna and is able to detect a human hand at a distance of an inch through the plywood and plastic top of the spectrum bar.
Acknowledgements We would like to thank Toyota Motor Sales USA for their financial support of this project, through the Toyota TAPESTRYgrant program. The TAPESTRY program is administered by the National Science Teachers Association. Thanks also to the Fluke Corporation for providing the Insight XST thermal imager at a substantial discount.
Members of the 2007-8 Senior Integrated Science class building this exhibit were: Drew Basile, Justin Deaton, Zach Dutch, Jonathan McClure, Ben Riedlinger, Pender Sessoms, Katherine Taylor, Jordan Walker, and Mara Whichard. Teacher: Jeff Regester.
Links
Senior Integrated Science course homepage at Greensboro Day School
Greensboro Day School
Mr. Regester's homepage
Natural Science Center of Greensboro
Toyota TAPESTRY grants program for teachers
Parallax, Inc., makers of the BASIC Stamp microcontroller
Fluke, Inc., makers of the Insight XST thermal infrared camera