Color Spectrum

What we see


determines what is
interpreted
 Isaac Newton
 first to study
 using
, showed sunlight is made of

Spectrum
 spread of

(low freq -> high freq)
 White light

 white objects appear
and colored
objects appear
 all colors combine to
 black is the
; it
all visible frequencies
 black objects
all light
otherwise you couldn’t see them; some
light
Color by Reflection


Color of objects due
Light is
(like a tuning
fork)
 once excited to vigorous motion,
send out their
in all
directions

Different materials have different natural
frequencies for absorbing and emitting
radiation
 resonant frequencies
,
light is
 frequencies below
,
light is
 reemited light
materials
 light
medium which it came
if
=

Most
of some
the rest
 e.g. if an object
light frequencies and

If an object
it will be the

If a material
on it, it
and
most visible
green,
light of
as the light that
the light that
,
NOTE: an object can
present in the illuminating light
 The perceived color of an object is
 depends on
 Best light to determine color =

Color by Transmission
Color of
depends on the
color of the
 Material in glass that
colored light =
 Electrons in pigment atoms
of certain frequencies
 Light of other frequencies
in the glass
 Energy is
,
glass

Mixing Colored LIGHT
White light
 comes from
 ALSO comes from mixing just
 Divided into three regions:

freq (
),
freq (
freq (
)

 Combinations
 red & green =
 red & blue =
 green & blue =


),
Complementary Colors

When two colors are
 yellow +

+ green

+
 Not all the
; some
 part that is
 i.e.
, reflects
upon an object is
is
from
on pigment that absorbs
Fig 28.10

Lighting objects with
 shadow of object will
light it is
 Objects will not
primary color
of
Mixing Colored Pigments
Mixing
and
is ENTIRELY
different from
 pigments reflect a
 Color mixing by
is used with
pigments in
and

and
mixed absorbs all colors
except

 Color mixing by
is used in

primary colors


Why the sky is blue
Atoms and molecules behave like
and
waves

,
the frequency
of light it will

sent in
 Most UV light
by
 Some UV light
and is
by particles and molecules in

scattered the most
 BUT our eyes
; our
eyes
 we see a


Increased
allows
  sky is
 after rains,
 sky appears

and other
to
,
and sky is
when there are
White clouds produced by combination of
waves caused by
Why Sunsets are Red

When light passes thru thick atmosphere,
light of
while light of
@ sunset, light reaches us thru
 more

remains in sunlight
 Sun gets

Water




a pale
to nearly all
Absorbs and resonates
Resonate somewhat to

of red light
 Red taken from
=
Atomic Spectra

Spectroscope analyzes

All elements
 The
and
of light
can be analyzed on a
 Combination and magnitude found on
line spectrum
 Each element has
=