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REHS Study > Light > Flashcards

Light Flashcards

1
Q

what is a standard candle measurement

A

amount of light given off from a standard candle. it’s the most standard measure of intensity of a light source

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2
Q

what is a foot candle measurement

A

measure of the amount of light striking an area of 1 sq ft from one foot away

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3
Q

What is a luminous flux

A

the amount of light coming from a source, or the quantity of light emitted

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4
Q

what is the lumen unit

A

a unit used to specify the quantity of light required to illuminate 1 square food of reflective

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5
Q

what is used to measure lumens

A

a photographic light meter

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6
Q

what is a lambert

A

the brightness of a surface emitting or reflecting one lumen per square centimeter

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7
Q

darker colors absorb (more/less) light than lighter colors

A

darker absorb more light

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8
Q

which color is known to be the most pleasing and restful to the eyes

A

green

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9
Q

if a light source of 30 foot candles is directed a gray wall, 60% of the light will be reflect (40% absorbed) therefore ______ foot lamberts is reflected and ____ foot candles is absorbed

A

18 foot lamberts reflected

12 foot candles absorbed

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10
Q

approximately what percent of light is reflected off the following colors

white
pink, yellow, light blue
medium blue
red

A

white 90%
pink, yellow, light blue 65%
medium blue 35%
red 15%

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11
Q

a good contrast is considered between __- an d___ percent

A

60 and 80%

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12
Q

what is the formula for contrast and what would be the contrast between a yellow background and a medium blue object

yellow - 65%, medium blue 36%

A

background reflection - object reflection
65-36=29

29/ background contrast x 100
29/65 x 100 = 44.6 % contrast

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13
Q

visibility depends on the ______ between an object and background

A

contrast

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14
Q

what are the two types of glare

A

direct glare from a bright light source

reflected glare caused by specular reflection (reflection off a shiny surface)

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15
Q

what is an example of specular reflection

A

the sun reflecting off the ocean water

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16
Q

the best lighting for studying is a combination of ______ and _______ lighting

A

direct and indirect lighting

17
Q

what type of light produces soft shadows

A

diffused light (light reflected off walls or floors)

18
Q

what type of light produces sharp, dense, direct shadows

A

direct lighting

19
Q

what is an e.g. of highly diffused light and what is it useful for

A

an overcast or cloudy day, little or no shadows are produced

great for photography

20
Q

what three factors are needed for proper lighting

A

illumination (foot candles)
brightness (food lamberts)
contrast

21
Q

the intensity of illumination on a surface varies _______ as the square of its distance from the light source

A

it varies inversely

22
Q

what is the recommended foot candles for a normal classroom

A

50

23
Q

does poor lighting cause eye damage?

A

no, just fatigue and stress

24
Q

is fluorescent lighting more or less efficient than incandescent lighting

A

more efficient

25
Q

a 40 watt fluorescent light produces nearly ____ more times light than a 60 watt tungsten light bulb

A

4 times more

26
Q

how does a fluorescent bulb work

A

electrical current goes through mercury vapor creating an arc that produces uv light. the uv light excites the fluorescent chemicals which coat the inside of the bulb.

27
Q

the buzzing noise commonly heard from fluorescent lighting is from the ______

A

transformer or ballast

28
Q

the transformer or ballast converts _____ into _____

A

house hold light into a high voltage

29
Q

what are disadvantages to fluorescent lighting

A

produces a cooler light which makes skin look pale and pictures look green

30
Q

fluorescent lighting forms ________ in the air. is this beneficial or negative?

A

negative ions

beneficial, good for human body, makes air smell clean and help pollutants fall out of the air

31
Q

what is infrared light

A

the lower wavelength light spectrum.

32
Q

what are some uses of IR light

A

to keep food hot
chemical spectroscopy
enamel drying
dehydrating textiles or paper

33
Q

what are the negative effects of IR light

A

may cause eye injury (produces cataracts)

can burn skin

34
Q

what is UV light

A

the high wavelengths of light

35
Q

what can UV light be used for

A

as a disinfectant

36
Q

what does LASER stand for

A

light amplification stimulated emission radiation

37
Q

what is LASER

A

a high intensity light at a single wavelength

38
Q

how can a laser be dangerous

A

direct exposure to the eye can cause blindness

REHS Study (20 decks)

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