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Calculate the speed of a water wave when waves 5.0 m apart
pass by at 40.0 waves per minute
Chapter 16
Light
Light•The range of frequencies of
electromagnetic waves that stimulate the retina
of the eye
Electromagnetic Wave•Transverse waves made up of pulses
moving through space that affect both electric
& magnetic fields
Spectrum•An ordered
arrangement of many frequencies or
wavelengths of waves
Electromagnetic Spectrum•An ordered
arrangement of all the electromagnetic waves
Ray•The straight line
path of a light wave
Incident Ray•A ray striking a
surface
Transmitted Ray
•A ray passing through a substance
Reflected Ray•A ray bouncing off
of another substance
Speed of Light•First Determined by Ole Roemer by observing the
moons of Jupiter from opposite ends of Earth’s
orbit.
Speed of Light•Correctly determined by
Michelson by reflecting light from a spinning
octagonal mirror.
Speed of Lightcvac = 299,792,458 m/s
For most calculations:
c = 3.00 x 108 m/s
Light Velocity Formula:
c = f
Calculate the frequency of electromagnetic
waves at:600.0 nm150 m45.0 cm
Calculate the frequency of IR
light at:900.0 nm
Luminous•Anything that emits light
•Sun, light bulb, etc
Illuminated•Anything that reflects light
•Moon, mirror, wall, etc
Luminous Flux (P)
•The rate at which light is emitted
Lumens (lm)•The unit of luminous flux
Light from a bulb or source is emitted spherically from the
source
We are usually interested in the illumination of a
certain area
Illuminance (E)•The illumination of
a surface
Lux (lx)•The unit for illumination
•lx = lm/m2
Luminous Intensity (I)
•The magnitude of the light source
Candela (cd)•Candle power of
the unit for luminous intensity
Luminous Intensity Formula
I
d2E =
Luminous Flux Formula
P
4d2E =
Determine the effect on illumination of a wall if a light source is moved
from 30.0 to 120 cm away from the wall.
Calculate the illumination on a
surface 2.0 m away from a bulb emitting
1600 cd.
Calculate the illumination on a
surface 3.0 m away from a bulb emitting
2700 cd.
Transparent•Substances that allows
light to be clearly transmitted through
them
Translucent•Substances that allows light to be transmitted,
though not clearly, through them
Opaque•Substances absorb or reflect all light striking
them
Color• A perception caused when cones in the eyes are excited
by certain frequencies or wavelengths of
electromagnetic waves
Luminous Colors
Primary Colors•Red
•Blue
•Green
Secondary Colors•Colors produced by mixing primary colors
Secondary Colors•Yellow = Red + Green
•Cyan = Blue + Green
•Magenta = Red + Blue
Complimentary Colors
•Two colors that when mixed produced white
light
Complimentary Colors
•Red + Cyan
•Blue + Yellow
•Green + Magenta
List the three primary colors &
list each’s complementary
color.
Illuminated Colors
Dyes•Molecules that
absorb certain wavelengths of light;
thus reflect others
Dyes•Dyes are made up of molecules which are too small to be seen with a microscope
Dyes•When dissolved, form colored solutions that allow light to pass through
Pigments•Materials that absorb certain wavelengths of light; thus reflect others
Pigments•Pigments are made up of particles large enough to be seen with a microscope
Pigments•When dissolved, form suspensions that reflect light and are opaque
Primary Pigments
•A pigment that absorbs a primary color
Primary Pigments
•Yellow
•Cyan
•Magenta
Secondary Pigments
•A pigment that absorbs two primary colors; thus reflect the third
Secondary Pigments
•They are the primary colors: red, blue, & green
Thin Film Interference•Constructive &
destructive effects of interference causing a
rainbow appearance on a thin film
Thin Film Interference
•Wavelengths are reinforced when the film
is ¼ , ¾ , 5/4 , etc
Electromagnetic waves are transverse with vibrations like
sin waves vibrating at 360o from the ray
Polarized Light•A light wave
vibrating in only one direction
Polarized Light•Can be produced by passing regular light through a polarized