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Light intensity

  1. Sep 27, 2008 #1
    I'm doing a report for biology about the relation betweem light intensity and photosynthetic rate. My results showed that as light intensity decreases, so does oxygen production.

    I said in my discussion that light rays that must travel longer distances will lose energy and appear dimmer than rays that travel shorter distances.

    Is this correct?
  2. jcsd
  3. Sep 27, 2008 #2

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    I'm afraid not.

    Light rays don't lose energy with distance. The apparent intensity of a light source does decrease with distance, but that's because the light is spreading out to cover a larger area.
  4. Sep 27, 2008 #3
    So a more appropriate conclusion would be that the rays are more concentrated when they are closer to the plant?
  5. Sep 27, 2008 #4


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    Can you describe the experiment a little more. What type of light source did you use? What did you actually change ... the power of the light source, or the location of the light source?

    Typically, light rays are more concentrated closer to the source of the light. Move the plant away from the source, and the light becomes less concentrated (i.e. dimmer) at the plant.

    This assumes you're not using lenses to focus the light, or a laser where the light intensity is fairly constant over a large distance.
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