Electromagnetic Wave Assignment

Georgia Perimeter College

Getting Started:

  1. Read your course notes on Electromagnetic Waves.
  2. Read your textbook, Chapter 12, p. 281-308 and 13, p. 309-337 for additional information.
  3. Open the web pages listed in the web links section of the course outlines to see the interactive java tutorials, animations, illustrations, and additional information on this topic.

Instructions:
  1. Do NASA exercise on Radio Waves.

    2. Do demonstrations, problems, and questions given in the course notes.

  2. Put a clear plastic or glass, rectangular dish on an overhead. The deeper and bigger, the better. Put just enough water in it to make waves. Too deep and the light won't get through well enough, too shallow and the effects won't show. On one end, use a ball on a toothpick or stick and make waves! Notice that the waves travel from the start to the other side at a constant speed, no matter how fast you make your waves. Speaking of fast-notice that the faster you make waves, the shorter the distance between them; frequency goes up as wavelength goes down.

    3.  
  3. Pick the wavelength of your favorite radio station and find the wavelengths of the signal. How big is it compared to you!?

    4.  
  4. Come up with a mnemonic for the bands of the spectrum.

    5.  
  5. What part of the visible spectrum is the longest in wavelength?
    Hint: it is right next to Infrared.

    6.  
  6. What part of the visible spectrum has the shortest wavelength?
    Hint: It comes right up to the Ultraviolet part of the E-M spectrum.

    7.  
  7. Take the shiniest, undented bottom of a soda can outside. Aim it at the sun.
    Using your finger or a small thin piece of paper the size of a matchstick, move the end towards the center of the 'mirror'. When you get light on the end, move the finger or stick directly out and in from the mirror center until the light is most concentrated.
    You've found the focal point or focus of the mirror.
     
    If the mirror was more perfect, that that of a telescope mirror, you'd actually get an image (see Optics section). This image is called a real image because you can actually see it, or at least capture its energy. No energy to capture at the location, virtual. Energy there, real.
     
    Oh, and you might feel a tiny bit of heat out of that focal point of the soda can but nothing to harm yourself with. Presumably polished well it can make little flame out of dry grass for when you are out in the desert and need some fire.

    8.  
  8. Put a spoon or ruler in a clear glass of water, or in an aquarium, at an angle. The more extreme the angle and the longer the ruler/spoon, the more the obvious will be the bending of the object.
     
    Alternatively, use a laser or tight-beam LED flashlight beam and shine it into the water.
     
    It helps to have a white surface on the bottom of the clear glass container. Then you can see refraction of the light at the place where water and air meet, and reflection of the beam at the bottom.
     
    If you can shoot the beam into the aquarium from the bottom and continually increase the angle from the perpendicular, eventually you will reach an angle at the air/water interface that changes the light path as a flat mirror instead of a refractor. You can also see that by looking up into the glass aquarium from the bottom and looking more and more from directly upwards towards the sides. Above you see things above the water, to the edges of the top surface you see a mirror-like surface. Swimmers may recall this impression as well.

    9.  
  9. The simplest demonstration of diffraction of waves around an object, and interference, is in your own hands! Bring your thumb and pointer finger together in front of any light source. As you bring your fingers closer and closer but not touching, you will see them 'grow' with a dark region forming between them. At some point the dark region will form stripes parallel to your fingers' skin. These stripes are the bright and dark interferences of the light being bent around the sharp edge of your two fingers!

    10.  
  10. What are the differences between E-M and mechanical waves?

    11.  
  11. Name and describe the different parts of the E-M spectrum. Include in your answers the wavelength sizes, frequency size, and typical uses of each part.

    12.  
  12. Draw a wave and label its various parts.

    13.  
  13. What are the three ways of changing light's direction and describe in one word each what the process does to a beam or wave of light.

    14.  
  14. Wavestown. Label the spectrum chart at the bottom (1-7), and then match the items in the picture to the electromagnetic spectrum.
    Image courtesy of NASA.

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Content provided by Mr. Larry Krumenaker, GPC

Page created by Pamela J.W. Gore
Georgia Perimeter College,
Clarkston, GA

Page created December 4, 2006