Chapter 15 - Lighting Flashcards
Candlepower or candela
unit of luminous intensity approx equal to the horizontal light output from an ordinary wax candle
Luminous flux
quantity of light emitted by a light sourceAbbreviation: Φ PhiUnit: lm Lumen
Luminous intensity
quantity of light that is radiated in a particular direction. This is a useful measurement for directive lighting elements such as reflectors. It is represented by the luminous intensity distribution curve (LDC).Abbreviation: ΙUnit: cd Candela
Illuminance
quantity of luminous flux falling on a surface.It decreases by the square of the distance (inverse square law). Relevant standards specify the required illuminance.Illuminance: E(lx) = luminous flux (lm) / area (m2)Abbreviation: EUnit: lx Lux
Luminance
only basic lighting parameter that is perceived by the eye
It specifies the brightness of a surface and is essentially dependent on its reflectance (finish and color). Candela per square meter
Abbreviation: LUnit: cd/m2
There are two types of glare
direct and reflected
What is the rating to evaluate direct glare?
VCP (visual comfort probability)
For most situations, the critical zone for direct glare is in the area above a ___ angle from the light source
45
____ occurs when a light source is reflected from a viewed surface into the eye
reflected glare
If the reflected glare interferes with the viewing task, it is also called a ________
veiling reflection
In addition to daylight, there are four types of light sources:
incandescent
fluorescent
high-intensity discharge
light-emitting diodes (LEDs)
Efficacy is a measurement of ____/____
lumens/watt
You want more or less lumens per watt
more
______ lamp consists of tungsten filament placed within a sealed bulb containing an inert gas. when electricity is passed through the lamp, the filament glows, producing light.
incandescent
An MR-16 lamp is a low-voltage, ______
multifaceted mirror reflector
MR-16s have a narrow or wide beam?
narrow
_____ is one type of incandescent lamp. Light is produced by the incandescence of the filament, but there is a small amount of a halogen, such as iodine or bromine, in the bulb with the inert gas
tungsten-halogen
tungsten-halogen
greater efficacy than standard incandescent
more compact
light is more blue/white
low-voltage is in the class of _____
incandescents
main disadvantage of low voltage?
transformer is required to step down the line voltage. this results in a bulkier luminaire and higher initial cost
fluorescent lamps
mix of an inert gas an slow-pressure mercury vapor
three types of fluorescent lamps
preheat, rapid start, and instant start
typical shape of fluorescent bulb?
tubular
high efficacy, low initial cost, long life available in a variety of color temps although most people think of them as being too “blue”
fluorescent lamps
many incandescent bulbs are being replaced with
compact fluorescents
______ lamps produce light by passing an electric current through a gas or vapor under high pressure
High Intensity Discharge (HID) lamps
three types of HID lamps
mercury-vapor, metal-halide, and high-pressure sodium
typical lamp for outdoor lighting and industrial applications?
mercury-vapor
long lamp life but poor color rendering
typical lamp for high-ceiling spaces where long life and high efficacy are desirable and in retail uses where point source control an excellent color rendition are needed?
ceramic metal halide
LED
Light-emitting diodes
LEDs are a class of _____
solid-state lighting
disadvantages of LED
upfront cost and relatively lower efficacies
Semi-direct lighting
majority of light down, small amount up
direct-indirect lighting
light goes up and down equally
common commercial lighting system
task-ambient
task-ambient
provides general background illumination level with separate light fixtures used at individual workstations or wherever light is needed
this can be done with desk lamps or directed spot lights
semi-indirect
most light goes up
most common type of light fixture for residential lighting
surface-mounted
_________ is a measure of how well one source renders the color of an object when compared with the same object lighted with a reference source of similar chromaticity whose rating is 100
color rendering index (CRI)
CRI index is rated from ____ to _____.
1 to 100
light switches are shown on
the RCP
Electric lighting and the cooling it requires typically account for __-__% of a commercial building’s total energy use and can sometimes range up to __%
30-40% and can be up to 50%
One of the problems with using daylighting, especially with large, high windows on the south side of a building, is the resultant glare and heat gain of direct sun. What is an effective way to solve this problem?
By using a light shelf
what is a light shelf?
horizontal surface placed above eye level that reflects direct daylight onto the ceiling while shading the lower portions of the window and interior of the roomit also distributes the light more evenly from the window to the back of the room
___ is expressed as a percentage, is the ratio of the indoor illuminance at a point on a horizontal surface to the unobstructed exterior horizontal illuminance
Daylight factor (df)
