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Activity Number 23 - UV And Sunglasses
To show that some sunglasses block a high percentage of UV radiation.
- UV meter
- pencil and pad
- several pairs of sunglasses (students can test their own)
- Take a UV reading with the UV meter in direct sunlight and record the value.
- Remain in direct sunlight. Rest one of the sunglass lenses on the UV meter over the black sensor button. Make sure that the button is completely covered by the lens. Do not touch the sensor with your fingers.
- Wait a minute for the UV Index to adjust and record the new reading. Continue to test the remaining pairs of sunglasses. Record all measurements on your sheet.
- Calculate the percent UV-B passing through sunglasses as follows:
Percent UV-B Passing through Sunglasses = (UV Index with Sunglasses ÷ Direct UV Index) x 100 percent
Points for Discussion
This test only shows approximately how well a pair of sunglasses protect your eyes from UV-B. Accurate UV testing for sunglasses can only be conducted by an optometrist or ophthalmologist.
UV-A is also harmful to the eye. When buying sunglasses, it's wise to check the label for the degree of protection from both types of UV.
You may want to visit the Health Canada web site at www.hc-sc.gc.ca and navigate to the It's Your Health fact sheet series. Two fact sheets are of particular interest: Sunglasses and Preventing Skin Cancer.
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