Lighting

Question 1

Lumens

Answer 1

Measurement of luminous flux (lighting at the source).

Question 2

Luminous flux

Answer 2

Lighting at the source.

Question 3

Illuminance

Answer 3

The density of luminous flux on a surface
(remember: the brightness of an illuminated surface)

Question 4

Luminance

Answer 4

The light emitted or reflected from a surface to the eye.

Question 5

Foot candle (fc)

Answer 5

Measurement on the receiving surface (light striking 1 sf, 1 ft from a candle).

Question 6

Coefficient of Utilization (CU)

Answer 6

The ratio of luminous flux reaching the work plane to the flux emitted by lamps.
Accounts for efficiency, room size, proportions, and surface reflectances, typically ranging from 0 to 1 (or 0-100%). Higher CU values indicate more effective, energy-efficient designs

Question 7

Inverse Square Law (Lighting)

Answer 7

Going twice as far from the source results in 1/4 the amount of light.

Question 8

Efficacy

Answer 8

A measure of a light source’s efficiency (lumens/watt).

Question 9

Glare

Answer 9

Sensation produced by brightness causing annoyance, discomfort, or loss of visibility.

Question 10

Direct glare

Answer 10

Results from a high brightness ratio or an insufficiently shielded light source.

Question 11

Visual Comfort Probability (VCP)

Answer 11

Measures the expected percentage of people to experience visual comfort.

Question 12

Indirect glare

Answer 12

Reflections of light sources on glossy surfaces.

Question 13

Veiling Reflection

Answer 13

Reflected glare that reduces contrast, making tasks harder to see.

Question 14

Light Pollution types: Tresspass, Sky Glow, Clutter

Answer 14

Trespass: A neighbor’s lights shining onto your property.
Sky Glow: Overall light pollution affecting an entire area.
Clutter: Excessive groupings of bright lights.

Question 15

Daylighting

Answer 15

Bringing the most light into the darkest part of a room.

Question 16

DF (Daylight Factor)

Answer 16

The ratio of daylight illuminance indoors to outdoors under an overcast sky.

Question 17

Daylighting Controls

Answer 17

Used to turn lights off or dim them when daylight is sufficient.

Question 18

Relationship of energy savings on lighting to HVAC

Answer 18

3 watts saved on lighting equals 1 watt saved on HVAC cooling.

Question 19

Azimuth

Answer 19

Location of the sun relative to due south.

Question 20

Altitude

Answer 20

The height of the sun in the sky.

Question 21

Zenith

Answer 21

Point directly overhead.

Question 22

Nadir

Answer 22

Point directly below.

Question 23

Color Rendering Index (CRI)

Answer 23

Scale from 0-100 measuring how accurately a light source renders colors.

Question 24

Correlated Color Temperature (CCT)

Answer 24

The color the light appears, measured in Kelvins.

Question 25

Kelvins (K)

Answer 25

Unit used to measure Correlated Color Temperature (higher = cooler tones).

Question 26

Ballast

Answer 26

An electrical device that limits the electric current to a fluorescent or HID lamp.

Question 27

Incandescent lamps

Answer 27

High CRI (100) lamps with high heat for low output (low efficacy).

Question 28

Halogen

Answer 28

In incandescent family, but filament gets hotter and burns brighter.

Question 29

Fluorescent lamps

Answer 29

Tube coated with phosphors inside, much lower heat, higher efficacy.

Question 30

Phosphors

Answer 30

Powders that coat the inside of a fluorescent tube to kick out light.

Question 31

High Intensity Discharge (HID)

Answer 31

Requires a ballast and includes Metal Halide and High Pressure Sodium lamps.

Question 32

Metal Halide

Answer 32

A cool light HID lamp based on an excited gas. Remember: cold, metalic lighting)

Question 33

Mercury vapor

Answer 33

Supplanted by Metal Halide lighting.

Question 34

High Pressure Sodium

Answer 34

Very efficient, warm light HID with very low CRI (~20). Mnemonic: think of warm salt lamps

Question 35

Low Pressure Sodium (LPS)

Answer 35

Not used because its CRI is extremely low.

Question 36

LEDs

Answer 36

Solid state lighting that sheds heat through convection.

Question 37

Luminaire

Answer 37

A ceiling mounted light fixture.

Question 38

Photometric curve

Answer 38

Describes the spatial properties of a lamp’s light.

Question 39

Grazing light

Answer 39

Light from an angle that shows more texture on a surface.

Question 40

Zonal Cavity Method

Answer 40

Determines the number and distribution of light fixtures required.

Question 41

Room Cavity Ratio (RCR)

Answer 41

(2.5 x total wall area) / area of work plane.