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.
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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