How Do You Calculate Light Absorption by Water Per Unit Depth?

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SUMMARY

The calculation of light absorption by water per unit depth is determined using the absorption coefficient (alpha) measured in reciprocal centimeters. The absorbance (A) of a water layer is calculated by multiplying alpha by the thickness of the water layer in centimeters. The intensity of light decreases according to the formula I = I0 * exp(-A) or I = I0 * 10^-A, where I0 is the initial intensity and d is the distance traveled in water. This relationship highlights the significant absorption of UV and infrared light compared to visible light.

PREREQUISITES
  • Understanding of light absorption principles
  • Familiarity with the concept of absorbance in physics
  • Knowledge of exponential decay functions
  • Basic grasp of the water absorption spectrum
NEXT STEPS
  • Research the water absorption spectrum for different wavelengths
  • Learn about the calculation of absorbance using the Beer-Lambert Law
  • Explore the effects of depth on light intensity in aquatic environments
  • Investigate the implications of light absorption on aquatic photosynthesis
USEFUL FOR

Students in biology and physics, researchers studying aquatic ecosystems, and anyone interested in the interaction of light with water.

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Homework Statement


I am currently doing a biology honours project at university and have been stumped by a fairly basic physics hurdle. I need to know the equation to calculate the amount of light absorbed by water/unit depth. I have tried to find the equation all over but cannot find anything. I am sure i did this in A-Level physics but i really can't remember -_-

Any help would be greatly appreciated
Thanks


Homework Equations





The Attempt at a Solution

 
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The light absorption in water depends on the wavelength of the light. It is fairly law for the visible light but strong for UV and infrared. See at
http://upload.wikimedia.org/wikipedia/en/7/72/Water_absorption_spectrum.png .

If you have the absorption coefficient alpha in reciprocal centimeters, multiply it by the thickness (in cm units) and you get the "absorbance" (A) of the water layer of the given thickness. The intensity of the light decreases with the ratio exp(-A) or 10-A, depending on the way alpha was given.
If the intensity of the incident light is I0, it decreases to I0*10-A after traveling through a distance d in water.

ehild
 
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