Light Energy and Its Sources Grade 8 Optics

12/26/20152 Natural and Artificial Light Natural light sources are objects that naturally emit light. (e.g. the sun, fireflies, the moon because it reflects) Artificial light sources are created by people. (e.g. light bulbs, camp fires, flashlights)

12/26/20153 Luminous and Nonluminous Luminous objects are objects that emit their own light. (e.g. the sun, a turned on flashlight) Nonluminous objects do not emit light, but only reflect light from other sources. (e.g. a book, a turned off flashlight)

Types of Light Incandescence Phosphorescence Electrical Discharge Fluorescence Chemiluminescence Bioluminescence

Incandescence objects - emit light at very high temperatures. e.g. filament light bulb, fire

Phosphorescence objects - emit light for some time after receiving energy from another source. e.g. Glow Stars, Numbers on some watches

Electrical Discharge -occurs when electricity passes through a gas and the gas particles emit light. e.g. Neon Sign

Fluorescence -is the process of emitting light while receiving energy from another source. Fluorescent tubes take advantage of electric discharge and phosphorescence. e.g. fluorescent lamp

Chemiluminescence - is the process of changing chemical energy into light energy with little or no change in temperature e.g. Glow Sticks

Bioluminescence -is a living object that can make itself luminous using a chemical reaction. e.g. fireflies, glow worms, angler fish (like in Finding Nemo), some plankton