Types and Sources of Light Pollution

There are many different types and sources of light pollution. Light pollution can mean visible light disruptions from a flooding of too much man-made light (as in the example of the city lights); it can also mean a lack of light – again, city lights take away a form of natural illumination and replace it with an artificial means; and it can also mean changes to light that cannot be seen. Light that cannot be seen is found on the radio-wave spectrum. When people talk about light pollution they tend to mean one of five specific types:

1. Over-illumination: This is caused by misuse of lights. Lights that are left on, or even street lamps that aren’t adjusted for daylight savings time, can cause millions of barrels of oil to be wasted. It can have the immediate effect of raising utility costs in an area as well as disrupting natural sleep patterns.

2. Glare: Glare is a two-fold problem in which lights are reflected off surrounding surfaces so that the light scatters and causes vision problems. It doesn’t interfere with night vision, but makes it difficult to identify and place objects.

3. Light clutter: Light clutter is a uniquely man-made issue and it stems from poor placement design. A cluster of business lights, or streetlights, can create a contrast illumination that interferes with night vision and illumination. It can also be strong enough to throw off the natural nocturnal systems of animals.

4. Sky Glow: This is a term used to refer to the almost dome-like cover of light to city areas. The light that is escaping from street lamps, signs, homes and businesses goes up to change the quality of light in the atmosphere, and it bounces back down to the city from the atmosphere. It can affect natural growth patterns, and the ability of planes to navigate at night too.

5. Light Trespass: Not only is this a form of pollution but it is also a crime in many areas. Light trespass refers to unwanted light entering someone’s property. It could be light from a sign coming into a residential area or any similar circumstance.

Resources:
http://www.conserve-energy-future.com/types-causes-and-effects-of-light-pollution.php