Stem measuring Albedo with the Digital Light Meter




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STEM



Measuring Albedo with the Digital Light Meter




  1. Press POWER to turn on the meter.

  2. Use LUX/FC to select lux.

  3. Remove the photo detector cap and place the detector horizontally face up.

  4. Press RANGE to find a suitable range.

  5. In making measurements, pressing HOLD stops further measurements. Pressing HOLD again cancels the hold mode.

  6. Avoid casting shadows on surfaces when making measurements.




Surface

Incident illuminance, I

Reflected illuminance, R

Albedo = R/I

88 brightness Xerox paper










Black construction paper










Water, normal incidence










Snow










Concrete










Asphalt










Soil










Turf

































www.umassk12.net/ipy

A STEM ED Program at the University of Massachusetts, funded by the National Science Foundation and supported by the

Climate System Research Center in conjunction with the International Polar Year




Some questions to ponder.


  1. When forests are cleared, the soil exposed sometimes has a smaller albedo than the trees that were there. What effect does that have on the local temperature?

  2. What is the effect of wearing dark clothes in strong sunlight rather than lighter colored clothing?

  3. When sunlight shines on a pine forest, what effect will multiple scattering in the trees have on the albedo?

  4. What effect do clouds have on the albedo of the earth?

  5. What effect does dust in the atmosphere have on the albedo of the earth?

  6. What effect does a large volcanic eruption have on the albedo of the earth?

  7. Cities commonly are warmer than the surrounding regions. What are some possible reasons?

A comment on photocopy paper brightness:


Photocopy paper is labeled with a brightness value, typically about 90. This is a number defined by the paper industry that is not directly related to albedo. A standard lamp provides light incident at 45º to the normal, and the reflected light is measured coming off at perpendicular to the surface. This is compared with the light reflected by a standard magnesium oxide tile. The brightness value can exceed 100 for some papers.


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