Light And Lighting

Question 1

Define illuminance

Answer 1

The amount of luminous flux per unit area.

Aka quantity of light on a certain surface

Question 2

Define luminance

Answer 2

The intensity of light emitted from a surface per unit area into your eye

Question 3

Define luminous flux

Answer 3

The measure of brightness of a light source in terms of energy being emitted

Question 4

Measuring daylight factor

Answer 4

The percentage of lux inside the building compared to what is available outside for a standard overcast sky

Question 5

Uniform standard sky for Britain

Answer 5

5000 lux for heavily overcast sky

Question 6

CIE standard sky

Answer 6

The luminance steadily increases above the horizon

Question 7

Define sky component

Answer 7

The light received directly from the sky

Question 8

Define externally reflected component

Answer 8

The light received directly by reflection from buildings and landscape outside the room

Question 9

Define internally reflected component

Answer 9

The light received from surfaces inside the room

Question 10

What device measures light?

Answer 10

Light meter/ photometer

Question 11

The Waldram diagram

Answer 11

A specially scaled grid representing half the hemisphere of sky

Question 12

PSALI

Answer 12

Permanent supplementary artificial lighting of interiors

Lighting design to provide illuminations that appears to be of good daylight character

Question 13

Incandescent lamps

Answer 13

Produce light by heating substances to a temperature

Question 14

Discharge lamps

Answer 14

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

Question 15

Luminous efficacy

Answer 15

The ability of a lamp to convert electrical energy to light energy end is measured by the ratio of light output to energy input

Question 16

Colour temperature

Answer 16

1700 k orange low pressure sodium lamps

15,000 k-27,000k clear blue poleward sky

Question 17

Correlated colour temperature

Answer 17

The absolute temperature of a perfect radiator when the colour appearance of the radiator best matches that of the light source

Question 18

Colour rendering

Answer 18

The ability of a light source to reveal the colour appearance of surfaces

Question 19

Colour rendering index

Answer 19

A number that indicated the accuracy by which a lamp shows surface colours

Question 20

Tungsten filament lamps

Answer 20

Passing an electric current through a filament of metal and raising the temperature to white heat

Question 21

Define luminaire

Answer 21

The light fitting that hold or contains a lamp

Question 22

British zonal system

Answer 22

BZ system classifies luminaries into 10 classes. BZ1 downwards light, BZ10 upwards light

Question 23

Utilisation factor

Answer 23

The ratio of the total flux reaching the working plane compared to the total flux output of the lamps

Question 24

Glare

Answer 24

The discomfort or impairment of vision caused by an excessive range of brightness

Question 25

Glare rating

Answer 25

An index or numerical measure of discomfort glare which enables glare to be assessed and acceptable limits recommended

Question 26

Albedo

Answer 26

The measure of natural light from exterior surfaces into interior spaces

Question 27

Pros and cons of daylight

Answer 27

``` Pros Good colour rendering Improve mood Influence sleep patterns Reduce need for artificial lighting ``` ``` Cons Lack of control Glare Black hole effect Heat loss ```

Question 28

Order from best to worst energy consumption of lamps

Answer 28

1. Low pressure sodium lamps 2. High pressure sodium lamps 3. Mercury iodide lamp 4. High pressure mercury vapour lamp