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
