Farouk Hossen Opticians Ltd

Choosing your sunglasses

 

The ozone layer protects any form of life existing on earth against excessive exposure to ultraviolet sunrays (UVR). The thinning of the ozone layer has increased the UV rays reaching the earth's surface. It is then very important to protect yourself from the dangerous sunlight rays whether you are in a working environment or having fun outside, and this is very easy to do.

The best protection is to stay away from sunlight and wear protective clothing and a wide brim hat. Also, apply a sunscreen of skin protection factor (SPF) 15 or higher to all areas of exposed skin. This applies to adults as well as children, whose skin is more sensitive.

Your eyes also need protection against UV and intense light.

 

Light and UV rays

 

Light is a form of energy called electromagnetic energy. It travels through space like a wave. The electromagnetic spectrum is made up of wavelengths. Only one part of the spectrum is visible. It is perceived by our eyes as a gradation of colors ranging from purple to red, via blue, green, yellow and orange.

The sun is the earth's most important source of luminosity. It is also a powerful source of electromagnetic energy, outside the visible range of the spectrum. Only forty-five percent of the solar energy reaches the earth as visible light; the rest are invisible rays.

There are two types of invisible sunlight rays - the infrared rays (IR) and the ultraviolet rays (UVR). These rays are also absorbed by the eyes. The luminous infrared rays have broader wavelengths than visible light; these are thermal rays, that is, they are sources of heat. Half of the solar energy reaches the earth in the form of heat or infrared rays. The infrared rays carry less energy than visible light.

The earth's atmosphere absorbs a major part of the sun's ultraviolet rays. Only five percent of the solar energy reaches the earth in the form of UVR. Comparatively to visible light, these rays have a shorter wavelength but are a bigger source of energy. The UV band is divided in UVC, UVB and UVA. The atmospheric ozone layer absorbs the UVC rays, which thus cannot reach the earth's surface.

 

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