WHY IS THE OCEAN BLUE?

KEY CONCEPTS

  1. The color of the ocean is dependent upon the degree of organic material in it. The color ranges from green to blue.
  2. Coastal waters are almost always greenish in color because they contain more organic particles. These disperse light so that the wavelengths refracted are green and yellow.
  3. The deep blue color of the open ocean indicates an area that lacks abundant life.
 

MATERIALS

  • one large glass bowl.
  • one small mirror, 3" x 5" is suggested.
  • a flashlight
 
 

PROCEDURE

  
 
 

Activity

  1. Add water to the glass bowl until it is almost full.
  2. Place the mirror in the water at a 45° angle. You may need to place rocks behind the mirror to support it.
  3. Shine the flashlight through the water so that it reflects off the mirror and onto a white paper, screen, or wall.
  4. You should see an entire color spectrum reflected like a rainbow. This indicates that the fresh water is clean and does not absorb any of the colors of the spectrum. Lead the students through a discussion. Reinforce the concept that in order for only one color (in this case, blue) to be visible there must be something in the water that absorbs all of the wavelengths except blue.
  5. As an additional activity, slowly add table salt to the water and mix. Look for changes in the spectrum.
 
 

Assessment Ideas

  • Observations and conclusions should be entered in student journals or portfolios. Zap shot or Polaroid photos can be added to the journal and portfolio entries. Create a time-lapse or Hyperstudio Stack of the experiment
  
 
 

CROSS-CURRICULAR IDEAS

  • Chemistry: Add various known salt compounds to the water. Record which colors disappear from the rainbow. Record information in journals
  • Mathematics: Does the amount of a salt compound in solution affect the intensity of color? Measure out various amounts of salt and add them to the water. Is there a difference in the intensity of any colors of the spectrum? Create a data table and graph the results.
  • Geography: Are there chemical reasons that certain bodies around the world are named for a color, such as the Red Sea?
 
 

VOCABULARY

  • absorb: to take in and make a part of itself reflect - to throw back or be thrown back, as with light, heat, or sound
  • color spectrum: colors present in the spectrum of white light or visible light. The wavelengths of visible light extend approximately from the 4000 to 7000 A (1 A = 10 - 8 centimeters)
  • organic: relating to, or derived from living organisms.
  • spectrum: distribution of energy emitted by a radiant source, as by an incandescent body, arranged in order of wavelengths.
  • wavelength: the distance from any point in a wave, as in light or sound, to the same point in the next wave. (i.e. peak to peak)
  
 

SOURCE

  • Adapted from "Winds of Change" educational CD-ROM, Copyright Caltech and NASA/Jet Propulsion Laboratory