Lighting Exam 2

Lumens=

Lumens=

Light output

Lumens is…

The total amount of light emitted from a light source

More Lumens=

Less Lumens=

Brighter

Dimmer

The wattage of a light source does/doesn’t tell you how bright the light is

Doesn’t

Footcandle (FC) is

Unit of measurement

One foot candle is equal to…

The light produced by one candle at a distance of one foot away

Luminous Flux

Time rate of flow of light

Unit for Luminous Flux

Lumen

Luminous flux is total…

Light emitted from a source

Luminous intensity

Amount of flux (Lumens) contained within a solid angle

Luminous intensity is the…

Amount of light in a given direction

Unit for luminous intensity

Candela (cd)

Illuminance

Flux (or Lumens) falling on a surface per unit area

Unit for illuminance

Footcandle or lux (lx)

Exitance

Luminous flux density leaving a surface

Unit for exitance

Lumens/sqft or Lumens/sq meter

Luminance

Amount of light leaving a surface in a given direction

Unit for luminance

Candela/sqft or candela/sq meter

Inverse square law

Light is inversely proportional to the square of the distance from the source of the light

Cosine law for illuminance

The illumination of a surface is directly proportional to the cosine of the angle between the normal to the surface and the direction of incident light

The five metrics to describe lighting

Luminance, flux, exitance, illuminance, intensity

Symbol for Illuminance

E

Symbol for Flux

Φ

Symbol for intensity

I

Symbols for Exitance

M

Symbol for Luminance

L

The density of light (or illuminance) on a given surface is a function of the ___________________ and ___________________ of the light source from the surface.

Distance and angle

What is considered the longest day of the year

Summer solstice

Horizontal light shelves help to minimize direct light into the space and allow light to bounce further into the space. Which orientation do horizontal light shelves have the biggest benefit

South

If two different light sources(LED and incandescent) have the exact same lumen output (600lm), will they also use the same amount of wattage?

No, the wattages will be different