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Activity Number 7 - An Experiment

Purpose

To show that the rate at which the sun's energy is absorbed is affected by the colour of a material.

Materials

  • 2 thermometers
  • One white or very light coloured piece of cloth
  • One black or dark piece of cloth (Note: the two pieces should be the same type of material.)
  • Watch or timer
  • Graph paper
  • Sunny day (or a heat lamp as a substitute source of energy)

Method

Record the initial temperature on each thermometer. Make sure that the temperatures on the 2 thermometers are the same. Wrap each thermometer with a different colour of cloth and place both in bright sunlight. Note the temperatures at 5-minute intervals until the mercury seems to have stopped rising. Then graph the results of the temperature over time for each sample. Did the temperature rise faster when the thermometer was wrapped in the light-coloured cloth or the dark-coloured cloth?

Observations

The rise in temperature was more dramatic when the thermometer was wrapped in dark cloth.

Conclusion

Dark-coloured materials absorb the sun's energy more completely and therefore more rapidly than light-coloured materials. Some of the energy is reflected back by lighter colours.

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