Sunglasses by benbenzhou

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									      Sunglasses


2007 CBCJ Class Item
        Purpose of Sunglasses

•   Protection from UV light rays
•   Comfort to eyes in constant sun
•   Keep eyes from tiring out
•   Protection from dust particles
•   Fashion
       Ultraviolet Radiation
• Ultraviolet light (UV) – short wavelengths
  of light that can cause harm to our eyes
• Two categories of UV light – UVA (longer
  wavelengths) & UVB (shorter wavelengths)
• UVB rays have been found to cause more
  eye damage than UVA. However, a good
  pair of sunglasses should protect against
  both types of UV light.
 Recommended UV Standards
• Sunglasses must block 99% of UVB rays.
• FDA recommendation: 99-100% of UVA
  and UVB radiation. The label should read
  either UV 400 or 100% UV protection.
• UV-blocking: term refers to sunglasses
  that block 99% of UVA and UVB rays
• Check the label on the sunglasses; it
  should state the protection percentage.
Background Info on Lenses

    The darkness does not
     affect the ability of the
        lenses to protect
         against UV light.
     However, darkness will
      determine how mush
     visible light gets seen.
              Types of Lenses
• Plain Lenses – uniformly tinted throughout; come in a
  variety of colors
• Blue Blockers – usually amber colored; block blue light;
  ski goggles
• Single Gradient Lenses – tinted darker at the top than
  the bottom; driving
• Double Gradient Lenses – tinted darker at the top and
  bottom and lighter in the center; sailing, skiing, &
  tennis
• Polarized and Anti-Reflective Lenses – designed to
  reduce reflected glare; water sports, biking, & driving
• Photo-chromatic Lenses – darken and lighten in
  response to amount of light available
• Flash and Mirror-Coated Lenses – have mirror-like
  finish (silver, colored, iridescent); coating adds
  appearance; scratches easily
           Lens Materials
• Polycarbonate – durable, lightweight
  plastic; super-strong and impact-
  resistant; composes most sport
  sunglasses
• CR-39 – plastic used mostly in
  prescription-grade lenses
• Glass – durable; heavy; breaks easily
• The FDA requires all sunglasses to within
  an impact test.
   Background Info on Color
The color of the lenses does not affect the
     blocking of UV light, either. Color only
    determines which colors will be seen by
   the viewer. Color coated lenses tend to
   scratch easier and loose their color than
  lenses that are dyed. Some color coated
     lenses have a scratch-resistant layer
     added on them by the manufacturers.
                    Colors
• Gray – reduce brightness; don’t distort color
• Brown/Amber – reduce glare; distort color
• Yellow – reduce haze from blue light; sharpen up
  the view; cause more color distortion
• Green – reduce glare; filter out some blue light;
  provide good contrast between objects
• Orange – have best contrast enhancement at
  depth perception; distort color
• Rose – good for water sports or outdoor activities;
  provide good contrast for objects against blue and
  green backgrounds
• Blue - offer no real benefits; mainly cosmetic
          Polarized Lenses
• Some models have polarized lenses.
• The purpose of polarized lenses is to
  reduce the glare caused by light
  reflected from polarizing surfaces (such
  as water) and skylight.
• Polarization can be especially useful
  when fishing, as the ability to see
  beneath the surface of the water is
  crucial.
        Frame Composition
• Frames need to be both sturdy and
  comfortable.
• When purchasing sunglasses, check to
  ensure that the frames are not bent or
  damaged.
• They should be wide enough not to press
  on the temples and long enough to rest
  on the ears.
                   Cost
• Price has little to do with the
  performance of a pair of sunglasses.
• Sunglasses that are effective and
  reliable can be inexpensive to
  moderately priced.
• For the contest, read the situation
  carefully. Check to see of cost is a factor
  in ranking the class.
                Reminders
•   UV radiation (block UVA and UVB)
•   Types of lenses
•   Materials that compose lenses
•   Colors of lenses
•   Frame composition
•   Cost

								
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