Lighting Flashcards
(12 cards)
What are the characteristics of a tungsten filament bulb?
Glass bulb with metal filament which glows when electric current flows through
Temperature can get up to 2204 degrees
Light is incandescent
Spectral emission is continuous
Inert gas controls evaporation
Poor efficiency
What are the characteristics of a gas discharge bulb?
Electric discharge jumps between gas atoms, exciting them to a higher energy orbit - excess energy on their return is a photon
Better efficiency than tungsten filament
Hard to manufacture
Spectral emission is on a line spectrum (only discrete atoms respond, so only certain wavelengths seen)
What are the characteristics of a tungsten halogen?
Contains tungsten filament, inert gas and halogen
Halogen cycle causes longer life (burnt off filament particles are redeposited by halogen)
Good efficiency
Higher luminous efficiency
What are the characteristics of compact fluorescent lights?
Longer life
Less energy used
What are the characteristics of a light emitting diode (LED)?
Electrical current flowing through semi-conductor causes illumination
Small
Long life
Switches fast
Power efficient
Physically robust
Low maximum and storage temperature
Needs DC power only, and low voltage
What are the types of luminaire light distribution?
Obstruction
Diffusion
Refraction
Reflection
Direct
Indirect
What do polar curves show?
Luminous intensity
(Direction and area of light covered)
Which British Standard covers electrical luminaires and lighting units? What types of safety does it cover?
BS EN 60598
Mechanical, electrical and thermal safety
What is generalised lighting?
Regular array of luminaires give an even spread of illuminance
E.g. in an office or factory
Flexible but wasteful
What is localised lighting?
Illuminance adjacent task, with reduced illuminance away from the task
Nicer aesthetic
What is local lighting?
Task lighting - luminaires at the task
What laws specify suitable lighting in certain environments? E.g. test room
Health and Safety at Work Act 1974
Factories Act 1961
CIBSE 1984 Code for Interior Lighting
