Light Energy andIts Sources Grade 8 Optics

04/21/23 2

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)

04/21/23 3

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 LightIncandescence

PhosphorescenceElectrical Discharge

FluorescenceChemiluminescence

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