READ: Electromagnetic Spectrum

READ: Electromagnetic Spectrum

Introduction  

When you walk outside on a sunny day, the only kinds of radiation you can detect are visible light, which you can detect with your eyes, and infrared light, which you feel as warmth on your skin,but if you’ve ever gotten a sunburn your body has been damaged by UV light from the sun.  Sunlight consists of all the different kinds of light. Fortunately, Earth’s atmosphere prevents most of the harmful radiation from reaching Earth’s surface.   

Electromagnetic Radiation   

Most electromagnetic radiation (energy that travels in waves) on Earth comes from the sun. Like other waves, electromagnetic radiation is characterized by certain wavelengths (the distance between two peaks on a wave).

Different wavelengths have different amounts of energy and wave frequencies (the number of waves that pass a fixed point in a given amount of time) . Electromagnetic waves with shorter wavelengths have higher frequencies and more energy. For example, to generate a higher-frequency wave in a rope, you must move the rope up and down more quickly. This takes more energy, so a higher frequency wave has more energy than a lower frequency wave.  

A Spectrum of Electromagnetic Waves 

Visible light and infrared light are just a small part of the full range of electromagnetic radiation which is organized on the electromagnetic spectrum. You can see the waves of the electromagnetic spectrum in the Figure below. At the top of the diagram, the wavelengths of the waves are given. Also included are objects that are about the same size as the corresponding wavelengths. The frequencies and energy levels of the waves are shown at the bottom of the diagram. Some sources of the waves are also given. 

• On the left side of the electromagnetic spectrum diagram are radio waves and microwaves. Radio waves have the longest wavelengths and lowest frequencies of all electromagnetic waves. They also have the least amount of energy.
  
• On the right side of the diagram are X- rays and gamma rays. They have the shortest wavelengths and highest frequencies of all electromagnetic waves. They also have the most energy.
  
• Between these two extremes are waves that are commonly called light. Light includes infrared light, visible light, and ultraviolet light. The wavelengths, frequencies, and energy levels of light fall in between those of radio waves on the left and X rays and gamma rays on the right.
  
• An easy way to remember the colors of visible light in order of increasing (lowest to highest) energy is the phrase ROY-G-BIV for red, orange, yellow, green, blue, and violet    
  

Lesson Summary   

• Electromagnetic radiation travels in waves through space or matter.
  
• Electromagnetic waves with shorter wavelengths have higher frequencies and more energy.
  
• The full range of electromagnetic radiation is called the electromagnetic spectrum. From longest to shortest wavelengths, it includes radio waves, microwaves, infrared light, visible light, ultraviolet light, X- rays, and gamma rays.   
  

CC-BY-NC-SA Utah State Office of Education. Material adapted from ck12.org

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