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anonymous

  • 5 years ago

PLEASE HELP!!!! The photic zone describes the region in which microscopic plant life receive enough light to survive. The photic zone goes to a depth where about 1% of the surface light still remains. Find the depth of the photic zone if the intensity of light (L) at a depth (d) in meters is given by L=L0e^(-0.028d), where L0 is the intensity of surface light. You may use the graphing part of your calculator for this question. Possible answers are: a. 124 m b. 134 m c. 144 m d. 154 m e. 164 m

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  1. anonymous
    • 5 years ago
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    I know you can use your calculator to find it but I have no idea how!!!

  2. anonymous
    • 5 years ago
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    L=100 per cent LO=1 per cent

  3. anonymous
    • 5 years ago
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    Ok, so how can I use that to solve? :( do I plug 0.01e^(-0.028x) into my calculator???

  4. anonymous
    • 5 years ago
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    You have an equation, the given, as they say. It has three unknowns -- not good. We have found two of the unknowns -- better. So now with one unknown you can solve for d.\[100percent=1percente ^{-0.028d}\]

  5. anonymous
    • 5 years ago
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    That makes much more sense, thank you. However im not so great at solving with exponents. How do I solve? This is how I would do it but I have noooo idea. 100 10,000 ---- = -0.028d ===> ------- = d ===> d= -357142.86 0.01 -0.028 I know its wrong but idk why :(

  6. anonymous
    • 5 years ago
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    You lost your e. You can't just arbitrarily take away your e. The plants would die from lack of sunlight.

  7. anonymous
    • 5 years ago
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    100 ---- = -0.028d should it start like that? 0.01e

  8. anonymous
    • 5 years ago
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    \[100=e ^{-0.028d}\]You have to use logarithms. Who knew marine biology was so much work.\[\ln 100=\ln e ^{-0.028d}\]

  9. anonymous
    • 5 years ago
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    So we just forget about the 0.01? does it turn into 100 ------ = d? that gives me d=-3571.43 -0.028

  10. anonymous
    • 5 years ago
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    There is no 0.01. The percentage signs cancel leaves 100 over one which is 100

  11. anonymous
    • 5 years ago
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    Ok, but I still solved and got -3571.43, which is not one of my answers. I dont understand!

  12. anonymous
    • 5 years ago
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    May be you did something wrong\[\ln 100=- 0.028d \ln e \]

  13. anonymous
    • 5 years ago
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    which gives me ln (100/-0.028)???? Im sorry I dont understand how to do these at all and I need to solve this problem

  14. anonymous
    • 5 years ago
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    You have the ability to find ln 100 and ln e on your calculator

  15. anonymous
    • 5 years ago
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    lne = 1 and ln100 =4.6, correct???

  16. anonymous
    • 5 years ago
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    yes

  17. anonymous
    • 5 years ago
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    so then I take 4.6/-0.028= -164.28, correct?

  18. anonymous
    • 5 years ago
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    Yes but depth is always positive, so absolute value (erase negative sign)

  19. anonymous
    • 5 years ago
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    So the answer is E, 164 m? Thanks

  20. anonymous
    • 5 years ago
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    You're pretty good.

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