Unit 1 Lighting Flashcards
What are the disadvantages of fluorescent tubes
- Contains hazardous materials (1) and require special disposal (1)
- Not dimmable (1) reduces the ability to control light levels (1)
- Requires uniform pattern of insulation (1) which restricts lay out (2)
What is the definition of light
Radiant energy that is capable of exciting the retina and producing visual sensation
What are the two types of lighting
- Natural lighting
2. Artificial lighting
Give a benefit of natural lighting
- Natural light in a building can provide natural illumination which reduce the for artificial lighting therefore saves on resources
What is artificial lighting
Light produced by human made device such as light bulbs
When is artificial lighting required
- where visual tasks may demand a higher level of illumination.
- To supplement day lighting when the level of illumination falls below the recommended value.
What are the differences between natural and artificial lighting
- light sources can be either natural or artificial
- Sun is the primary source of natural light, and light bulbs or lamps are artificial sources
- Light is a form of electromagnetic energy that in the case of natural light comes from the sun as the source and in the case of artificial light illuminates via energy from another source
Glare
- Bright objects result in glare
2. shopping centres adopted glare to produce a visually stimulating and pleasant environment
Direct Lighting
- Light falls from the luminaries on the ceiling directly onto the workplace
- glare suppression is important
- High energy efficiently is archived for the work area
Indirect lighting
- Light is directed to the ceiling and walls so that it illuminates the workplaces indirectly
- light is glare free
- workplaces can be arranged at random
- Lower energy efficiency
What is the purpose of lighting
- To enable the occupant to work and move about safely
- To enable tasks to be performed correctly and at an appropriate pace
- To create a pleasing appearance
What are solutions to combat poor lighting
- Improved overhead lighting
- Changing the paint colour of walls
- Placement of wok benches for natural lighting
What is luminous flux and what is it measured in
- The flow of light
- Measured in lumens
Note: A lamp receives watts and emits lumens (lm/W)
What is luminous intensity what s it measured in
- Ability of a source to emit light
2. measured in candela (cd)
What is luminance and what is it measured in
- Is a measure of the brightness of a surface as seen by the human eye
- Unit: Candela/m²
Illuminace (Lux)
- Amount if light falling on a surface where it is transmitted, absorbed or reflected
- Measured in lumens per sqm also known as lux
What is luminous efficacy
Efficiency with which the electrical power consumed is converted into light
For visual comfort and good optical performance, the following criteria apply what needs to be archived?
- Balanced arrangements of lights
- Suitable level of illumination (lux levels)
- Avoidance of glare and reflection
What is day light factor
The ratio of the light level inside a structure to the light level outside the structure
What is the inverse square law formula
E (Illuminance in lux) = I (Light source in cd) / d² (m)
What is the formula for cosine law of illuminance
E (Illuminance in lux) = I (Light source in cd) / d² (m) x Cos theta
Give examples of where domestic lighting is used ?
- Sitting rooms
- Class rooms
- Offices
Give examples of where outdoor lighting is used
- Shopping mall
- Clubs
- Factories
What factors are involved in lamp selection
- Luminous efficacy (lumen output / watts input)
- Rating (watts consumption)
- Mortality (rated life of the lamp)
- Lumen maintenance (lumen depreciation over life)
- Size (physical properties can affect optical efficiency of light control)
- Control gear type 9switching or dimmer)
- Colour appearance (Warm or cool)
- Starting, run up and re-start times
- Minimum starting temperatures
What are the 3 main categories of lamp
- Tungsten filament lamps
- Fluorescent lamps
- High-intensity discharge lamps
Each category has different operating characteristics. I.e. cost life span, colour, efficiency
Note Building regs require energy efficient lamps
What are the advantages of Incandescent tungsten filament lamps
- Low purchase price
- Excellent colour rendering
- Immediate full light when switched on
- Ease of dimming
What are the disadvantages of filament lamps
- Low efficacy – 8 to 15 l/W
- Short life, usually 1000 hours
- High running cost.
What are the advantages of florescent lamps
- Different blends of phosphor powder allow a choice of lamps of different colours, rendering and appearance properties
What are the disadvantage’s of fluorescent lamps
- Can take time for them to turn on and reach full light output
What are the advantages of Tungsten halogen (quartz halogen) lamps
1, Excellent colour rendering
- Immediate full light output when switched on
- Can be dimmed
- Life of 2000 to 5000 hours depending on type
What are the disadvantages of Tungsten halogen (quartz halogen) lamps
- Requires careful handling
2. Transformer required for extra low voltage lamps
What are the advantages of high pressure sodium lamps
- Very low running cost
- Very high efficacy
- Very long life
- Quick start
- Universal operating position
What are the disadvantages of high pressure sodium lamps
- High purchase cost
- Very poor colour rendering
- Requires 1.5 to 6 minutes time to run up to full output
What are the advantages of compact fluorescent lamps
- Low running cost
- Very good colour rendering with most lamps and some types giving excellent colour rendering
- Quick run up to full light output
- prompt start and restart
What are the disadvantages of compact fluorescent lamps
- Cant be dimmed
2. Excessive switching shortens life
Advantages of LED Lamps
- Varies in clour
- Low running cost
- Quick run up to full light output
- Prompt start and restart
- Universal operating position
Disadvantages of Led Lamps
Brightness and pattern of light often poorer
How can the day light factor be maximised
- Locate windows where they will receive the most day light (1) so they are not in the shade of other buildings (1)
- Increase size/number of windows (1) to increase sky component (1)
- Building is located in a position free from any obstructions (1) so that light into the building is not obstructed
