Chapter 15 Lighting

Question 1

What is candlepower (cp)?

Answer 1

The unit of luminous intensity approximately equal to the horizontal light output from an ordinary wax candle.

Question 2

What is a lumen (lm)

Answer 2

the unit of luminous flux; that is – a measure of the amount of visible light that the human eye can detect from a lamp or light source

Question 3

What is illuminance?

Answer 3

Describes the measurement of the amount of light falling onto (illuminating) and spreading over a given surface area

The density of luminous flux incident on a surface in lumens per unit area

Question 4

What variables are involved when determining the proper quantity and quality of light is a space?

Answer 4

What tasks are being preformed in the space

the age of the person preforming tasks

reflectances of the room

Question 5

In general, what is the illumination ratio between task lighting and general lighting for most local codes power budgets?

Answer 5

General lighting to be 1/3 illuminance of task lighting

Question 6

What are the considerations when determining light quality?

Answer 6

Glare, contrast, uniformity, and colour

Question 7

What are the two types of glare?

Answer 7

Direct glare: when a light source in the field of vision causes discomfort and interference with visual task
Reflected glares: when a light source is reflected from a viewed surface into the eye

Question 8

What is the visual comfort propability?

Answer 8

The visual comfort probability (VCP) - 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

Question 9

Where is the critical zone for direct glare?

Answer 9

45 degree angle

Question 10

What are veiling reflections?

Answer 10

When a reflected glare interferes with the viewing of a task.

it is an interaction between light source brightness, the position of the task, the reflectivity of the task, and eye position

Question 11

In terms of lighting, what is contrast?

Answer 11

The difference in illumination level between one point and nearby points

Question 12

In most situations, what should the brightness ratio be between a task and:

A) immediate surroundings
B) nearby general surroundings
C) remote surroundings

Answer 12

A) 1:3
B) 1:5
C) 1:10

Question 13

In addition to daylight, what are the 4 types of light sources?

Answer 13

Incandescent, fluorescent, high-intensity discharge (HID) , light-emitting diodes (LEDs)

Question 14

What is efficacy?

Answer 14

How efficient a light source is at converting electrical energy into Luminous Flux. It is the ratio of how many lumens are created for a given watt of electrical power consumed.

At 100% efficiency 1 watt of electrical power would produce 683 lumens.

Question 15

What is an incandescent lamp?

Answer 15

Tungsten filament placed within a sealed bulb containing an inert gas -when electricity is passed through, the filament glows

Question 16

What are advantages and disadvantages of incandescent lamps?

Answer 16

Advantages: inexpensive, compact, easy to dim, warm colour

Disavantages: low efficiency, short life, highheat out put

Question 17

What are fluorescent lamps?

Answer 17

A combination of inert gas and low-pressure mercury,

when the lamp is energized- a mercury arc is formed that creates ultra-violet light.

The uv light strikes the phosphor-coated bulb

causing fluoresce and produces visible light.

Question 18

What are the advantages and disadvantages to fluorescent lamps?

Answer 18

Advantages: high efficiency, relatively low costs, long life, variety of colour temps

Disadvantages: difficult to control precisely, expensive to dim,

Question 19

What is a high-intensity discharge lamp?

Answer 19

Produce light by passing an electric current through a gas or vapour under high pressure

Question 20

What is a light-emitting diode lamp? (LED)

Answer 20

A semi-conductor device that uses soild-state electronics to create light.

Question 21

What are the advantages and disadvantages to LED lamps?

Answer 21

Advantages: brightness, long life, low power consumption, no heat, controlled by a digital interface

Disadvantages: cost more, lower lumen output

Question 22

What are the 6 lighting systems?

Answer 22

direct: provide 90 to 100 percent of the light output on the task

semi-direct: provide 60 to 90 percent of the down and 10 to 40 percent of light toward the ceiling
direct-indirect: provide equal amounts of light up and down

indirect: throw from 90 to 100 percent al all light toward a reflective ceiling

semi-indirect: provide 60 to 90 percent of the light toward the ceiling and 10 to 40 percent of light toward the task

general diffuse (task ambient): provides a general background illumination level

Question 23

What are the methods lighting fixtures can be mounted / installed?

Answer 23

Surface mounted
Recessed
suspended
wall mounted
furniture mounted
freestanding
accessory

Question 24

How is Colour temperature in lighting measured?

Answer 24

A single number rating of their dominant colour based on the temperature in degrees Kelvin - lower the number, wormer the colour -higher the number, cooler the colour

Question 25

What is a lamps characteristic spectral energy distribution?

Answer 25

Measure of energy output at different wavelengths, or colours

Question 26

What is the colour rendering index?

Answer 26

CRI is a measure of how well one light source renders the colour of an object when compared with the same object lighted with a reference source of similar chromatically whose CRI is 100

Question 27

What is the process for designing a lighting installation?

Answer 27

Determine the function/visual tasks of the space as well as existing conditions

Select lamp type based on factors determine in fist step as well as colour rendition and economy costs

Select luminaire with technical and aesthetic aspects in consideration

Determine quantity and location of the luminaries

Question 28

What is the zonal cavity method?

Answer 28

A system that determines the number of luminaries required to provide a given footcandle level

using the efficacy of the lamp (lumen per Watt), the number of lamps in luminaire, the coefficient of utilization of the luminaire, gradual loss of light output over time (lamp lumen depreciation factor), luminaire dirt depreciation factor

Question 29

What is lamp lumen depreciation factor?

Answer 29

The gradual loss of light out put of lamps over time

Question 30

What is luminaire dirt depreciation factor?

Answer 30

Conditions under which a luminaire will be used, which affects the amount of dirt collected on the lamps overtime

Question 31

What is the coefficient of utilization (cu)?

Answer 31

A number used in zonal cavity method that represents how efficient the luminaire distribute the light from the lamps under various degrees of finish reflectivity of the floor, walls, and ceiling

Question 32

How may light switches are in a three way switch?

Answer 32

2 switches - the 3 in three way switch represents the number of conductors

Question 33

What does a photocell control do?

Answer 33

Dims electric lighting when it is not need due to maximizing day light. This can reduce perimeter energy by 50-60%

Question 34

What problems can daylight cause that need to be addressed when designing?

Answer 34

Unwanted heat gain or loss, glare, imbalanced lighting

Question 35

What is daylight factor (DF)?

Answer 35

The daylight factor is defined as the ratio of horizontal indoor to outdoor illumination by daylight under continuously overcast sky conditions, expressed as a percentage.

Question 36

What is recommend DF level for ordinary visual tasks and difficult visual tasks?

Answer 36

Ordinary: 1.5% difficult: 4%

Question 37

What 3 methods can be used to meet building code jurisdictions for power that can be used for lighting in a building?

Answer 37

Building area method: limits total power used by giving a maximum allowable power in watts per sqft

Space-by-space method assigns LPDs to common space types

Energy cost budget method: determines energy cost for specific building design through computer simulation

Question 38

What is lighting power density (LPD)?

Answer 38

total power used in a building by giving maximum allowable power in watts per square foot