Light Flashcards
what is a standard candle measurement
amount of light given off from a standard candle. it’s the most standard measure of intensity of a light source
what is a foot candle measurement
measure of the amount of light striking an area of 1 sq ft from one foot away
What is a luminous flux
the amount of light coming from a source, or the quantity of light emitted
what is the lumen unit
a unit used to specify the quantity of light required to illuminate 1 square food of reflective
what is used to measure lumens
a photographic light meter
what is a lambert
the brightness of a surface emitting or reflecting one lumen per square centimeter
darker colors absorb (more/less) light than lighter colors
darker absorb more light
which color is known to be the most pleasing and restful to the eyes
green
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
18 foot lamberts reflected
12 foot candles absorbed
approximately what percent of light is reflected off the following colors
white
pink, yellow, light blue
medium blue
red
white 90%
pink, yellow, light blue 65%
medium blue 35%
red 15%
a good contrast is considered between __- an d___ percent
60 and 80%
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%
background reflection - object reflection
65-36=29
29/ background contrast x 100
29/65 x 100 = 44.6 % contrast
visibility depends on the ______ between an object and background
contrast
what are the two types of glare
direct glare from a bright light source
reflected glare caused by specular reflection (reflection off a shiny surface)
what is an example of specular reflection
the sun reflecting off the ocean water
the best lighting for studying is a combination of ______ and _______ lighting
direct and indirect lighting
what type of light produces soft shadows
diffused light (light reflected off walls or floors)
what type of light produces sharp, dense, direct shadows
direct lighting
what is an e.g. of highly diffused light and what is it useful for
an overcast or cloudy day, little or no shadows are produced
great for photography
what three factors are needed for proper lighting
illumination (foot candles)
brightness (food lamberts)
contrast
the intensity of illumination on a surface varies _______ as the square of its distance from the light source
it varies inversely
what is the recommended foot candles for a normal classroom
50
does poor lighting cause eye damage?
no, just fatigue and stress
is fluorescent lighting more or less efficient than incandescent lighting
more efficient
a 40 watt fluorescent light produces nearly ____ more times light than a 60 watt tungsten light bulb
4 times more
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.
the buzzing noise commonly heard from fluorescent lighting is from the ______
transformer or ballast
the transformer or ballast converts _____ into _____
house hold light into a high voltage
what are disadvantages to fluorescent lighting
produces a cooler light which makes skin look pale and pictures look green
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
what is infrared light
the lower wavelength light spectrum.
what are some uses of IR light
to keep food hot
chemical spectroscopy
enamel drying
dehydrating textiles or paper
what are the negative effects of IR light
may cause eye injury (produces cataracts)
can burn skin
what is UV light
the high wavelengths of light
what can UV light be used for
as a disinfectant
what does LASER stand for
light amplification stimulated emission radiation
what is LASER
a high intensity light at a single wavelength
how can a laser be dangerous
direct exposure to the eye can cause blindness
