WHAT IS LIGHT
LIGHT
� Artificial Light � Light that people have created � Examples: Light bulb, glow
stick � Natural Light
� The most abundant and cheapest form of light
� Examples: Sun, fire � Radiation
� This does not require matter
PRINCIPLES OF LIGHT
� 1. Light is a form of energy! � 2. Light that is absorbed by a surface can be
transformed into thermal energy, electrical energy or chemical energy.
INCANDESCENT SOURCES
� Object heated to a point where it emits light
� Inefficient � 95% of energy is lost as heat
� Energy Transformation: � Electrical Energy Thermal
Energy Visible Light Energy � Examples:
� Light bulb, candle flame, fire.
FLUORESCENT SOURCE
� Under a black light, white looks like it is glowing.
� Fluorescence is ultraviolet light being absorbed and reflected by particles in fabric.
� Page #181 -Diagram
FLORESCENT ENERGY TRANSFORMATION
� Summarized � Ultraviolet Light Energy Energy Absorbed by
Particles Visible Light Energy
� Energy Pathway is: � Electrical Energy Energy Absorbed by mercury
particles Ultraviolet Light Energy Energy Absorbed by Phosphor Particles Visible Light Energy
COMPARISON Incandescent Florescent
PHOSPHORESCENCE SOURCES � Light energy is absorbed by
particles that can store this energy for awhile.
� The persistent emission of light following exposure and removal of source of radiation is called phosphorescence.
� Take longer to emit light and continue to glow for awhile after.
CHEMILUMINESCENT SOURCE � Light from a chemical reaction
� Light is produced when the reaction creates significant energy among particles. This results in visible light.
BIOLUMINESCENT SOURCES
� Light produced through chemical reactions in an animals body.
� These reactions create energy and thus a source of visible light.
WAYS TO REMEMBER � Phosphorescence = Phosphor coating makes it
glow � Chemiluminescence = Chemical Reaction � Bioluminescence = Biology, study of living things � Can we come up with a way to remember the
energy pathways for florescence? � E � M � U � P � V