Year 2 I1

Question 1

cornea

Answer 1

light enters the eye through the transparent outer membrane surrounding the eye

Question 2

Describe: the retina

Answer 2

passes through the focusing lens, and strikes the retina for form the optical image pattern

Question 3

Describe: the iris

Answer 3

(coloured portion of the eye) acts as a diaphragm to expand or contract the pupil.

Question 4

Describe the pupil

Answer 4

controls the amount of light that is allowed to enter the eye

Question 5

List four factors affecting visibility

Answer 5

size
brightness
contrast
time

Question 6

wavelengths of visible light

Answer 6

from 380 nm to 760 nm

Question 7

human eye is most responsive to

Answer 7

555 nm or yellow-green colour range

Question 8

Colour Temperature

Answer 8

or chromaticity is expressed in degrees Kelvin but not a measure of temperature, but rather a measurement of light quality
Low colour temp = warm colour below 3000K
High colour temp = cool colour above 4000K

Question 9

Color Rendering Index (CRI)
75-100 Excellent
60-75 Good
50-60 Fair
0-50  Poor

Answer 9

the ability of a light source to portray the colour appearance of objects accurately
Value from 0 to 100 where 100 is the best

Question 10

List 2 Light measurements

Answer 10

Luminous Flux quantity of light output

Luminous Flux density is the density of light flux or illumination

Question 11

1 Lux

Answer 11

is equal to 1 lumen per square metre

Question 12

Lighting equation 1

Inverse square law

Answer 12

E = l/d^2
E = illumination in lux
l = light intensity in candela
d = distance in metres

Question 13

Lighting equation 2

Cosine law of incidence

Answer 13

E = (I/d^2) x cos(theta)

Question 14

Luminous efficacy

Answer 14

is the ratio of the light output (lumens) to the power input (watts) Lm/W
with no losses 1 watt would produce about 683 Lumens

Question 15

List three factors that affect the Quality of light

Answer 15

Glare
Diffusion
Colour

Question 16

Two of the main causes of light loss

Answer 16

Lamp lumen depreciation

Luminaire dirt depreciation

Question 17

Light Shapes

Answer 17

Straight side = S Tubular = T
Flame = F Pear-shaped = PS
Globular = G Parabolic = PAR
Standard line = A Reflector = R

Question 18

Edison base

Answer 18

most common screw type

Question 19

Tungsten-halogen lamp

also called quartz halogen or quartz iodine

Answer 19

compact high-intensity
white light output
Used for projection, automotive, photocopying and floodlights
contains halogen gas the aids in the regenerative cycle
Lamp life 2500-3000
operates at 5 to 6 atmospheres must be contained in case lamp shatters

Question 20

Ballast function

Answer 20

provides the high starting voltage to ignite the tube
limits the current in the tube once the tube lights
in some short tubes only limits the current

Question 21

Fluorescent lamps are measured in 8ths

Answer 21

T8 is 8 8ths or 1 inch in diameter

Question 22

CFL

Answer 22

compact fluorescent lamp

can be used for replacement of a incandescent lamp

Question 23

Stroboscopic effect of fluorescent lamps

Answer 23

makes rotating machine appear stopped
use lead-lag ballasts operating in twin-lamp fixtures
connect lamp fixtures on different phases of a three phase system
electronic ballasts eliminates this

Question 24

Fluorescent lamps are classified

Answer 24

according to their start methods
preheat start not used much
instant-start
rapid-start

Question 25

Instant start or cold-cathode starting

Answer 25

has a step-up transformer to a sufficient magnitude to not have to pre-heat the cathode

Question 26

Slimline fluorescent is a instant-start

Answer 26

that has a switch incorporated in one of the lamp-holder sockets so that high voltage will not be present until lamp is fully seated

Question 27

Rapid-start cct fluorescent

Answer 27

eliminates three major shortcomings large, heavy ballast high strike voltage longer lamp life due to lower strike voltage

Question 28

Electronic ballasts

Answer 28

take low-frequency AC convert to DC convert to very-high-frequency AC. above 20kHz caution shock hazards high voltages can be above 347 V

Question 29

the wire used for end to end fluorescent fixtures install

Answer 29

must be not less than 600 V rated and 90 degrees Celsius

Question 30

List three types of HID lights

Answer 30

High-intensity discharge Metal halide Mercury vapour High-pressure sodium

Question 31

Describe Mercury Vapour Lamp

Answer 31

Must have ballast to strike small arc that vapourizes the mercury and permits striking of the main arc. 3 to 7 min starting Restart - restrike time is 4 to 6 min 24000 hour plus operation have a phospor coating that improves the colour by converting some UV radiation to visible light Letter code is H for Hg

Question 32

Describe Metal halide lamps

Answer 32

Shorter arc tube than Mercury vapour contains additional compound metals and halogen gas that improves efficacy and colour rendition of the lamp. first choice for good colour redition startup is 5 to 7 min restart and restrike can be as long as 15 min Shorter life span 15000 hrs letter code is MD or M

Question 33

Describe High-pressure sodium lamp

Answer 33

HPS different in that it has no starting electrode An arc tube that contains xenon gas and sodium-mercury amalgam Special circuitry in the ballast provides arc strike or 2500 v or more startup time of 3 to 4 min warm golden white restrike time is usually less than a min rated lifespan is 24000 can operate in any position without adverse effects on bulb letter code is S

Question 34

Letter shape codes for HID

Answer 34

``` B = bullet BT = bulged-tubular E = elliptical PAR = Parabolic aluminized reflector T = tubular ```

Question 35

H36BT-1000/DX

Answer 35

``` H for mercury vapour 36 for ballast type BT for shape 1000 for wattage DX for colour Deluxe colour ```

Question 36

HID Reactor ballast

Answer 36

only used with H and sometimes called a lag reactor ballast works only when supply voltage is high enough to strike an arc acts only as a choke seldom used in new install

Question 37

HID Autotransformer ballast

Answer 37

lag autotransfromer ballast PF .9 used with H lamps can not be used when supply voltage varies beyond plus or minus 5% to low or variations of voltage can keep lamp from striking

Question 38

HID auto-regulator ballast

Answer 38

constant wattage autotransformer ballast (CWA) With the combination of capacitor and autotransformer (reactor) give a PF .95 can handle voltage fluctuation of 40 to 50 % without extinguishing the lamp taps for two or more supply voltages used for all HID but most common for MH

Question 39

HID regulator ballast

Answer 39

secondary windings are electrically isolated from the supply windings superior to autotransformer in that it can hand plus or minus 13 % and voltage dips of up to 50 to 60% larger and more expensive

Question 40

HID HPS ballast

Answer 40

supplies high-voltage spike to augment the starting voltage because HPS bulb has no starting electrode. Electronic starting aid provided pulsed voltage with a peak of 2500 to 4000V