LOOKING AT LIGHT

Introduction

Researchers have been studying visible light and its properties for many centuries. However, because human eyes see only a small portion of the electromagnetic spectrum, its invisible forms were not discovered until more recent times.

The Greeks were probably the first to study visible light in a scientific way. They tried to explain such things as vision and color. Their discoveries inspired other researchers to use lenses and other instruments in order to find out how light worked and what it was made of. In 1665, Isaac Newton proved that white light was in fact a combination of many colors.

The invisible forms of electromagnetic radiation were first recognized by accident. In 1800, William Herschel was doing experiments to learn if light of different colors had different temperatures. One of his thermometers happened to be placed at the red end of the spectrum beyond the range of visible light. That thermometer showed a jump in temperature. Herschel realized that some new form of radiation was causing the temperature change. Not long afterwards, another scientist wondered if a new form of invisible radiation might exist at the opposite end of the spectrum. He was right. Inspired by these discoveries, more researchers took up the search, and many new forms of electromagnetic radiation, from radio waves to gamma waves, were soon identified.

Have you ever had an X-ray taken by your doctor? The discovery of X-rays in 1895 led to an interest in using different types of radiation for medical purposes. Today, X-rays, gamma rays, ultraviolet light, and other forms are all used in medicine, as well as for many other purposes.

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Your Task

For this WebQuest, your job is to investigate discoveries in the exploration of the electromagnetic spectrum. To demonstrate what you have learned, you will answer the questions included here. You will also complete one of the activities described at the end of this WebQuest.

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Process

Read through the following questions. Then research the Internet resources that are provided for you. As you explore the sites, look for answers to the questions. Keep a record of any sites where you find answers by noting the title and URL (Internet address). For example:

            (title) Technology Student Association
            (URL) www.tsaweb.org

1. Approximately when did Greek scholars begin to study light?
   
   
2. Who was the first scientist to study lenses in order to control light?
   
   
3. What instrument did Isaac Newton use to prove that white light was a combination of colors?
   
   
4. What form of light did William Herschel discover with his thermometers?
   
   
5. What form of light did Johann Ritter call “chemical rays”?
   
   
6. Who discovered X-rays?
   
   
7. How is ultraviolet light used in medicine?
   
   
8. At which end of the spectrum are temperatures the highest?
   
   

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Internet Resources

Visit the Web sites listed here to find information that will enable you to answer the questions. You may use additional sites if you wish. Be sure to keep a record of any sites you use.

• The Discovery of the Spectrum of Light provides a brief history of important developments.
  
  
• The Electromagnetic Spectrum uses NASA’s astronomy photos to show images obtained with the range of wavelengths in the spectrum, including infrared and gamma rays.
  
  
• Cool Cosmos covers basic information about the electromagnetic spectrum and offers links to a wide range of activities.
  
  
• Encarta: Wilhelm Conrad Roentgen is about the experiments that led to the discovery of X-rays.
  
  
• Cool Cosmos: Infrared Astronomy—Discovery of Infrared provides interesting information about uses for infrared light.
  
  
• Cool Cosmos: Ritter Discovers Ultraviolet Light tells the story of this important experiment.
  
  
• Discovery of infra-red light explains the simple experiment and describes how it can be done at home.
  
  
• Cool Cosmos: Classroom Activities—The Herschel Experience provides instructions for reproducing his work.
  
  
• Optical Research Associates: Optics for Kids—Science and Engineering explores light-how it can be controlled, how a lens works, and how light interacts with matter, among other topics.
  
  
• Light and Color offers links to many topics, including sources of visible light, whether light is particle or wave, and how lasers work.
  
  

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Activities

Several activities are described below. Complete one of these activities (your choice) to demonstrate the understandings you've gained by going on this WebQuest.

• Create a poster illustrating a common prosthetic device. Explain how it works.
  
  
• With your teacher’s help and using instructions at the following Web site, reproduce William Herschel’s experiment: http://coolcosmos.ipac.caltech.edu/cosmic_classroom/classroom_activities/herschel_experiment.html
  
  
• Do some research to learn about animals that can see wavelengths on the electromagnetic spectrum that humans cannot. Write a brief report on your findings.
  
  

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