Transcript Informal Presentation PPT

COLOR
MIHA LEE
Sun Light
Visible Light
 Color is the visual perceptual
property in humans.
 Typical human eye responds to
wavelengths to 300~700nm.
Three ways of Interaction
 Transparency
=> Transmission of light without scattering
 Translucency
=> Transmission of light with scattering
 Opacity
=> Absorption (and/or) Reflection
Color of material
 Color is the visible light that is
reflected or emitted by a material.
 Color as reflected (not absorbed) light
 Color as emitted light
Absorption & Emission of Light
=> Transition of Electrons
Indicator
 Indicators are usually weak acids.

HIn

H+ + In(In an acid solution)
(In a base solution)
 Le Chatelier’s principle
Tomato Juice
 Tomato has lycopene which has a lot of
conjugated double bonds.
 When lycopene undergoes chemical
reactions, the color of tomato juice will be
changed.
Color as Reflected Light
 Part of the white light is absorbed and the
rest of visible light is reflected.
 A substance absorbs some wavelengths of
visible light preferentially.
 Color of a substance depends on its
molecular structure.
 Organic dyes and pigments.
Color as Emitted light
 Usually, the absorbed light change into heat
in a substance.
 However, some special substances have an
ability to give off some specific color of
visible light in a certain condition.
 Fluorescence
 Phosphorescence
Flame Reaction
 Flame reaction is a reaction of some
elements.
 Those elements absorb heat energy in a
flame, and emit specific wavelengths of
visible light.
 Flame reaction is a kind of Fluorescence.
Flame Reaction
Size Quantization Effects
Fluorescent Lamp
Phosphorescence
 A process in which
light energy absorbed
by a substance is
stored and released
relatively slowly in the
form of light.
Glow in the Dark
Color
 A color of a substance depends on the
structure of its molecule or atom.
 The transition of electrons in electronic
orbital states shows the specific color.
 There are many substances that don’t have
colors because their transitions occur out of
the visible range.