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

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
a 40 watt fluorescent light produces nearly ____ more times light than a 60 watt tungsten light bulb
4 times more
26
how does a fluorescent bulb work
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
the buzzing noise commonly heard from fluorescent lighting is from the ______
transformer or ballast
28
the transformer or ballast converts _____ into _____
house hold light into a high voltage
29
what are disadvantages to fluorescent lighting
produces a cooler light which makes skin look pale and pictures look green
30
fluorescent lighting forms ________ in the air. is this beneficial or negative?
negative ions beneficial, good for human body, makes air smell clean and help pollutants fall out of the air
31
what is infrared light
the lower wavelength light spectrum.
32
what are some uses of IR light
to keep food hot chemical spectroscopy enamel drying dehydrating textiles or paper
33
what are the negative effects of IR light
may cause eye injury (produces cataracts) | can burn skin
34
what is UV light
the high wavelengths of light
35
what can UV light be used for
as a disinfectant
36
what does LASER stand for
light amplification stimulated emission radiation
37
what is LASER
a high intensity light at a single wavelength
38
how can a laser be dangerous
direct exposure to the eye can cause blindness