Definition:
Light pollution refers to the excessive and obtrusive form of artificial light. This can include sky glow and glare that is brought about by the scattering of light in the atmosphere by minute particles of dust or water.
Cause:
Light pollution results from outdoor lights aimed upward or sideways --- the light scatters in the atmosphere and reflects back to the ground. The result is sky glow. Particles in the atmosphere responsible for air pollution accentuate light pollution by increasing the amount of light scatter. According to the International Dark-Sky Association, light sources that emit blue light are particularly disruptive to night skies due to greater light scattering.
Effects:
According to the National Park Service, city lights as far as 200 miles away diminish views of night skies. Light pollution is a major concern for observatories as lights from urban areas compete with lights from stars and planets, reducing visibility of the objects that observatories study. This type of pollution also affects wildlife and plants. Night lights disorient hatching sea turtles, migrating birds and nocturnal animals. Lights attract insects, which may in turn interfere with pollination of nocturnal flowers. In humans, light pollution can interfere with natural circadian rhythms by preventing the production of melatonin, the chemical that regulates sleep patterns. Low melatonin levels have been linked to increased cancer risks.
Reduction:
There are ways to reduce light pollution, starting in your own neighborhood. Make sure outdoor lights reflect downward in what are called fully-shielded fixtures. Also consider exchanging high-wattage bulbs for dimmer ones and selecting warm-white lights with low emission of blue light. A great way to save energy and reduce trespassing light is to turn off outdoor lights unless needed.
There r five type of light pollution:
*Light trespass
*Over-illumination
*Glare
*Light clutter
*Skyglow
I guess ozone depletion is called as light pollution.. causes cutting trees. Prevention : planting many trees.
light pollution occurs when the lights emittes more amount of radiation due to which more amount of heat is produced
What?
Light pollution's stray light emitted from poorly designed and aimed lighting installations for advertising, business, security and street lighting. While some light is unavoidably reflected upward from illuminated surfaces, much of it spills outside the area that it is meant to illuminate creating glare,light-trespass and sky glow.
This stray light and the energy generated to produce it is wasted. It unnecessarily contributes to greenhouse emissions, and wastes money. Also, this wasted light does not necessarily contribute to safety nor enhance amenity. Very often it creates a nuisance. We do need outdoor lighting at night but there are better alternatives that save energy and improve the quality of nighttime lighting that also help to reduce sky-glow and preserve the night sky. Light pollution is much easier and cheaper to remedy than most other kinds of pollution!
Causes
Glare
A proportion of street-lights, car-yard and security lights are chosen and installed with little consideration for efficiency and aiming. Glare from these lights can shine directly into the eyes creating discomfort. This can make it difficult for the eye to adjust effectively to changing levels of illumination thereby compromising night vision.
Light Trespass
Uncontrolled light that spills outside the area that it is designated to illuminate and onto neighbouring properties. This often creates a nuisance, detracts from amenity and wastes energy and money.
Skyglow
Light that escapes upward from unshielded light fixtures or lights that are indiscriminately aimed upwards. This light is completely wasted, scattering in the atmosphere creating skyglow and detracts from the beauty of the starry sky at night. In particular, growing skyglow is compromising the effectiveness of many of the world's great astronomical observatories that provide for us a window to the universe!
Solution
Streetlights can be replaced with full-cutoff fixtures (all light directed downward - no light emitted upward) and fitted with energy efficient lamps. Sign-lighting should preferably be aimed down on signs-not upwards. Outdoor security, and display lighting should be fitted with quality shielded flood lights and fitted with efficient lamps directing light at the target area only. Residential BBQ floodlights can be shielded to minimize light trespass and up light. Also, avoid over lighting where possible.
In Australia this will save tens of million of dollars in electricity and hundreds of thousands tonnes of carbon dioxide emissions per year. In addition, efficient, quality, shielded outdoor lighting creates better illumination and contributes to safety. It also helps to bring the stars back to the night sky by reducing sky glow.
Lighting controls are increasingly adopted in many countries around the world with benefits in energy savings, and improved efficacy in lighting. In Australia we have good outdoor lighting Standards. Some councils comply while most business and private installations still ignore them. It's time for Australia catch up!
The Good
Full cut-off fixtures direct light below the horizontal. At top is one of the standard "cobra head" fixtures fitted with a flat glass. It aims light downward and sideways avoiding uplight and glare that improves the quality of lighting. The floodlight (bottom) is mounted in the horizontal position for security lighting and areas such as car yards and parking lots.
The Bad
These semi-cutoff lights are fitted with drop-lenses or refractors that emit a greater portion of their light sideways for wider road coverage but create more glare. They also send light upwards that contributes to skyglow. Full cut-off fixtures should be considered as an alternative. Mercury lights (bottom) are a bad choice. They are especially glary and inefficient compared to other lights and their used should be discouraged.
The Ugly
Intended to highlight advertising or "enhance" architecture, these globe-type and upward-aimed billboard lights can indiscriminately spray light everywhere. Badly aimed sign, business, and architectural lighting, are often placed so that a substantial portion of the light completely misses its target and adds to wasted light and sky glow. Post-top lights used for pathway and parkland lighting such as this globe-light waste light skyward. They should preferably be replaced with aesthetic alternatives that direct light below the horizontal.
its causes and prevention
