Lecture Fourteen - Light Pollution Flashcards
Give and describe the unit for measuring light intensity.
Lux
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
- LEDs
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.
400-600nm
What colour light do insects have visual sensitivity to?
Blue light
What is the main colour of light found in mercury vapour lighting?
Blue light
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?
Blue
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?
Balled lights
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?
Cloudy weather
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?
Green
Are Greater Horseshoe bats found more in dark or light areas?
Dark
Describe the characteristics of light shy species of bat.
- Late emerging
- Slow flyers
- Moth specialists
Describe the characteristics of light tolerant species.
- Early emerging
- Fast flyers
- Use early-emerging insects
Give two species of light shy bats.
- Horseshoe
- Long-eared
Give two species of light tolerant bats.
- Noctule
- Pipistrelle
What group of bats have been found to have more activity around lights than away from them?
Leisleri bats
What tones of light attract larger moths, noctuids?
Blue (LEDs)
What percentage of a brown long-eared bat’s diet is noctuid moths?
80%
Why could it be an advantage for bats to feed on moths around streetlights?
- Moths can hear echolocation cries of bats
- The drop-out response of moths is impaired by presence of light
- Moths could be easier to catch
What is the effect of Chironomid emergence in high or medium light?
Greater numbers of Chironomids emerging.
What is the effect of mayfly emergence in high lighting?
Won’t emerge at all in high lighting.
What is the effect of Trichotopert levels in high lighting?
Majorly reduced.
