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55 Cards in this Set
- Front
- Back
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How is white light produced? |
When a source emits approximately an equal amount of energy over the entire visible spectrum. |
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What is a Candlepower (cp)? |
the unit of luminous intensity approximately equal to the horizontal light output from an ordinary wax candle. (Metric version of this unit is called a candela) |
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What is a lumen? |
the unit of luminous flux equal to the flux in a unit solid angle of one steradian from a uniform point source of one candlepower. |
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What is Illuminance? |
The density of luminous flux incident on a surface in lumens per unit area. |
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What is luminance? |
the luminous flux per unit of projected (apparent) area and unit solid angle leaving a surface, either reflected or transmitted. |
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What is the difference between luminance and brightness? |
brightness includes the physiological sensation of the adaptation of the eye, whereas luminance is the measurable state of object luminosity |
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What is luminous intensity? |
the solid angular flux density in a given direction measured in candlepower or cancelas |
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What are the variables involved in selecting a level of illumination? |
nature of the task, age of the person performing it, reflectance in the room, and the demand for speed and accuracy when performing the task |
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According to the Illuminating Engineering society of north america, there are categories for illuminance for particular design conditions, what are they? |
Categories range for A to I, A represents the lowest values for general lighting in noncritical areas, and I represents requirements for specialized and difficult visual tasks |
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When a power budget is used for a project what are the recommended illumination levels for task areas and general light? (general rule of thumb) |
The general background (ambient) illumination be less than the task, about one-third of the task level |
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What are the considerations for the quality of a light? |
Glare, contrast, uniformity, and color |
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What are the two different types of glare and when do they happen? |
Direct glare: results when a light source in the filed of vision causes discomfort and interference with the visual task
Reflected glare: occurs when a light source is reflected from a viewed surface into the eye |
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What is the factor that was developed to evaluate direct glare? |
The visual comfort probability factor (VCP), is the percentage of people who, when viewing from a specified location and in a specified direction will find the situation acceptable in terms of discomfort glare. |
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What is veiling reflection glare? |
When the reflected glare interferes with the viewing task, they are caused by a complex interaction of light source and brightness, position of the task, reflectivity of the task and position of the eye. To avoid this have general background light and specific task lighting that can be moved around by the viewer. |
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What is contrast? |
the difference in illumination level between one point and nearby points. |
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What are the common brightness ratios between the task light and the surroundings? |
3:1 between the task and immediate surroundings
5:1 between the task and nearby general surroundings
10:1 between task and more remote surroundings |
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What are the three types of light sources in addition to daylight? |
incandescent, fluorescent, high-intensity discharge and LEDs |
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What is efficacy? |
The ratio of luminous flux emitted to the total power input of the source, it is measured in lumens per watt. It is an important measure of the energy efficiency of a light source. |
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What is an incandescent lamp? |
Consist of a tungsten filament placed within a sealed bulb containing an inert gas. When electricity is pass through the filament glows. They are designated by their shape followed by a number that indicates the diameter in eighths of an inch at the widest point. |
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What is an R type of incandescent lamp and its characteristics? |
Reflector lamp and it has a wide beam spread. Available in both flood and spotlight beam spreads. |
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What is an ER type of incandescent lamp and its characteristics? |
Elliptical reflector and it provides a more efficient throw of light from a fixture focusing the light beam at a point slightly in front of the lamp before it spreads out. Beam spread is slightly smaller than the R lamp. |
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What is a PAR type of incandescent lamp and its characteristics? |
A parabolic aluminized reflector lamp focuses the light in a tighter spread, with the light rays more parallel. Available in both flood and spotlight beam spreads. |
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What is an MR-16 lamp and its characteristics? |
A type of incandescent lamp, multifaceted mirror reflector. Many angles of beam spread are available but generally have the narrowest beam spread. |
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What are the advantages of incandescent lamps? |
inexpensive, compact, easy to dim, can be repeatedly started without a decrease in lamp life, have a warm color rendition, and the light output can be easily controlled with reflectors and lenses. |
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What are the disadvantages of incandescent lamps? |
Low efficiency, short lamp life, and high heat output. |
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What are fluorescent lamps? |
A type of lamp that contains a mixture of an inert gas, and low pressure mercury vapour. When the lamp is energized, the mercury forms an ultra violet light, and this invisible light strikes the phosphor coated bulb creating the visible light. |
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What are the three types of fluorescent lamps? |
Preheat, rapid start, and instant start, according to their circuitry. |
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What is the general shape and sizes of fluorescent lamps? |
They are produced in tubular shapes, normally straight but u-shaped and circular lamps are also available. They come in a variety of lengths with 4' being the most common. |
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What are the advantages of fluorescent lamps? |
They have a high efficiacy, relatively low initial cost, long life, and are available in a variety of colour temperatures. |
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What are the disadvantages of fluorescent lamps? |
I don't know. |
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What are High Intensity discharge lamps? |
They produce light by passing an electric current through a gas or vapour under high pressure. |
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What are the types of high intensity discharge lamps? |
mercury-vapor, metal-halide, and high pressure sodium |
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What are the advantages and disadvantages to a mercury- vapour high intensity discharge lamp? |
They have a long lamp life but poor colour rendering. Usually limited to outdoor lighting and industrial applications such as warehouses. |
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What are the advantages and disadvantages to a metal- halide high intensity discharge lamp? |
These lamps provide the best combination of features of the high intensity discharge lamps. They have colour rendering indexes between 60 and 90, high efficacy, and relatively long life. The main disadvantage is that they experience a large shift in apparent colour temperature over their life. |
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What are the different types of outer bulbs for HID metal halide lamps? |
Clear: used when optical control is required
Phosphor-coated: used for better colour rendition
Diffuse: specified in recessed downlight fixtures installed in low ceilings |
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What is the biggest disadvantage to HID lamps? |
They all require time to restart after being shut off or in case of a power failure. The lamp must first cool and then it takes time to warm up.
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What is an LED? |
A Light Emitting diode, a semiconductor device that used solid-state electronics to create light. |
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What are the advantages of LED lights? |
brightness, long life, low power consumption, produce no heat, can be controlled by a digital interface and can be manufactured to produce a number of colours or white light |
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What are the disadvantages of LEDs? |
Low efficacy and high cost |
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What are the main lighting systems? |
Direct, semi-direct, direct-indirect, general diffuse, semi-indirect, or indirect, tast-ambient
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What is the direct lighting system? |
provides all light output on the task. a recessed fluorescent luminaire is an example. |
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What is a semi-direct lighting system? |
puts majority of the light down and a small percentage towards the ceiling. They must be surface mounted or suspended |
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What is a direct-indirect lighting system? |
distribute light up and down about equally |
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What is an indirect lighting system? |
directs all the light toward a reflective ceiling, where the light illuminates the room by reflection |
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What is a task-ambient system? |
A common commercial lighting system that provides a general background illumination level with separate light fixtures used as individual workstations or wherever light is needed. |
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What are surface mounted fixtures? |
The luminaire is directly attached to the finished surface of the ceiling directing all or majority of the light into the space. They are usually used where there is not sufficient space above the ceiling to recess a fixture or where they are being added after the ceiling is constructed. |
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What are recessed light fixtures? |
Widely used in residential and commercial, usually limited to incandescent down lights because they can be located in the limited space between floor or ceiling joists. |
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What are suspended light fixtures? |
Luminaries that are dropped below the level of the ceiling. These can include direct incandescent or fluorescent fixtures, track lighting, indirect systems, chandeliers, and other specialty lights. |
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What is the colour temperature of a light source? |
The single number rating their dominant colour based on the temperature in degrees Kelvin. The lower the colour temperature is the warmer the light will be. As the temperature increases, the light become more blue and white. |
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What is CRI? |
The measure of how well one source renders the colour of an object when compared with the same object lighted with a reference source of similar chromaticity whose CRI is 100. Is is a number between 1 and 100. |
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What is the general light design process? |
1. determine the function of the space and the visual tasks to be performed (footcandle level) 2. select the lamp and luminaire types 3. determine the number and location of the luminaries |
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What are some existing conditions that might affect the lighting design? |
daylighting contribution, ceiling height, ceiling construction, the size of the room and other physical limitations. |
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What is the lamp lumen depreciation factor? |
The gradual loss of light output go the lamp over time. |
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What is the luminaire dirt depreciation factor? |
The amount of dirt collected on the lamps over time |
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What is the Coefficient of utilization (CU)? |
a number used in these calculations that represents how efficiently the luminaire distributes the light from the lamps under various degrees of finish reflectivity of the floor walls and ceiling. |
