Science Projects

Combating and Educating about Light Pollution

Glossary

Asymmetric Parabolic Reflectors - This describes the style of good quality floodlighting, often used to control light spill and light pollution. The reflector behind the discharge tube is shaped so as to throw the light away from the floodlight rather than simply below. (see diagram)

B.S. 5489 - This is the road lighting standard. It is split into several 'parts' each concerned with a different aspect of road and street lighting.

Discharge Tube - This is the part of the luminaire that actually produces the light. Its equivalent in the home would be the light bulb, or in a flood-light the halogen tube. The different type of gas used inside the discharge tube and the pressure of the gas, determines the colour of the light.

Example:

  • Mercury gives a bluish white light
  • Low Pressure Sodium, a yellow light
  • High Pressure sodium, a pinkish white light
  • Neon, gives red light

Discomfort Glare - This is the discomfort felt in the eye by intense light sources. This is sometimes experienced when driving when bright unshielded street lights cause eye strain, this may or may not impair vision.

Full Cut-Off (FCO) - This describes a type of luminaire that holds the discharge tube (source of light e.g. the 'bulb') high up within the fitting and only allows light to be emitted downwards. Sometimes these fitting as fitted with flat glass and so no light is emitted above the horizontal and light is strictly controlled. Sometimes they are fitted with shallow bowls or deeper bowls which has the effect of spreading the light more and causes some upward reflected light off of the bowl under the luminaire.

Glare Blindness - This is the blinding light frequently seen when oncoming cars have their headlights on full beam. This causes one to experience the glare in such a way that practically nothing else is visible. Similar effects are also seen when 'security' lights shine and one is unable to see anything due to the glare blindness.

HPS - High Pressure Sodium Lighting. These lights produce a pinky white light and the discharge tube also has sodium contained within it. The gasses within the discharge tube are at a higher pressure than the LPS discharge tubes.

LPS - Low Pressure Sodium Lighting. These lights produce the yellow lights seen throughout the UK road network. The discharge tube is quite long and has sodium in it which produces the yellow lighting.

Light Pollution - The scattering of unwanted light in the atmosphere caused by aerosols such as water vapour, dust and smoke etc...

Light Spill - The spreading of light in areas where the light is either unwanted or unintended.

Luminaire - The housing at the end of a lamp post that contains the light source, reflectors and switching gear.

Sky Beam - The use of a searchlight or similar lighting device that places an intense beam of light into the sky. Space flowers use powerful laser lights that can be controlled in such a way as to trace out shapes and patterns in the night sky.

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