Flashcards in Lecture Fourteen - Light Pollution Deck (40)
Give and describe the unit for measuring light intensity.
Measurement of how humans perceive light.
What is the increase in lux from 1923-1999 in Britain?
0.8 - 13.1
What used to be the major source of light, and has now mostly been faded out?
Mercury vapour light
What are the cons of mercury vapour light?
- Expensive to make
- Not very energy efficient
- Wet bulbs break
What were mercury vapour lights replaced by?
Low-pressure sodium lighting
What were low-pressure sodium lights replaced by?
- High-pressure sodium lighting
What can be said about the light emitted from low pressure sodium lighting?
It is almost monochromatic, emitting 600nm pure orange light.
What is the difference between light emitted from low pressure and high pressure sodium lighting?
- Low pressure is almost monochromatic
- High pressure has a greater spectral range.
Give the range of optimum light perception for mammals.
What colour light do insects have visual sensitivity to?
What is the main colour of light found in mercury vapour lighting?
In what kind of lighting are colours most difficult to identify?
Mercury vapour lighting
Why did we move away from low pressure sodium lighting?
It is difficult to identify facial expressions from a distance.
What is the main colour of light found in LEDs?
Why are dark patches between light installations avoided by light engineers?
Takes some time for drivers' eyes to adjust to changing light levels.
Why could dark patches be useful ecologically?
Act as a dark passageway for animals that don't like light.
What causes sky glow?
Reflective light hitting a hard surface, or escaping upwards from a light fitting.
When is sky glow worse?
- Cloudy nights
- When ground is wet
What is an ecological effect of sky glow?
Could affect navigation.
What type of light design is most likely to produce sky glow?
Give the proportions of light destinations for balled lights.
- 50% waste
- 10% glare
- 40% productive
How could light pollution in the environment affect the migration of animals?
- Many use celestial cues when migrating
- Cannot see stars
- Could cause difficulties in migration
What colour lighting do birds use to calibrate their magnetic compass?
What colour light disrupts the compass?
- use blue-green light
- red light disrupts this
In what particular weather are birds attracted to lights?
How can we change lighting on gas extraction rigs?
Place filters over the lights to filter out some wavelengths.
What colour light for birds causes the
a) Most encounters?
b) Least encounters?
a) Most encounters with white light
b) Least encounters with blue lights.
Why can't blue lights be put in oil rigs?
If you cut yourself, can't see the bleeding.
What colour lights are attractive to fish?
Are Greater Horseshoe bats found more in dark or light areas?