How is Light Produced? PDF

How is Light Produced?  NATURAL VS. ARTIFICIAL LIGHT Light sources can be classified as either: – Luminous – produces its own light – Nonluminous – does not produce its own light Ex, Sun = luminous Moon = nonluminous (only reflects the sun’s light)  INCANDESCENT LIGHT...

How is Light Produced?  NATURAL VS. ARTIFICIAL LIGHT Light sources can be classified as either: – Luminous – produces its own light – Nonluminous – does not produce its own light Ex, Sun = luminous Moon = nonluminous (only reflects the sun’s light)  INCANDESCENT LIGHT light that is produced by an object that is at a very high temperature. An incandescent light bulb produces light when an electric current passes through a filament wire causing it to heat up and glow Because incandescent bulbs produce so much heat, they are very inefficient and only 5% of the electrical energy is converted to light.  ELECTRIC DISCHARGE An electric discharge is a method of producing light in which an electric current passes through the air or another gas such as neon.  FLUORESCENT LIGHT Light emitted by some substances when they are exposed to electromagnetic radiation. Electrons collide with a gas such as mercury vapour inside the tube causing the release of ultraviolet light. The inside of the tube is coated with a white powder called a phosphor. This is a substance that glows after being exposed to photons of ultraviolet radiation. ADVANTAGES: A compact fluorescent bulb is more efficient (20% to 30% converted to visible light) longer life produce less heat DISADVANTAGES: mercury creates environmental and health problems relating to disposal  USES OF FLUORESCENCE Fluorescent dyes are often added to detergents to make clothes ‘brighter’ Highlighters contain fluorescent ink  PHOSPHORESCENCE AND CHEMILUMINESCENCE Phosphorescence is the ability to store the energy from a source of light and then emit it slowly over a long period of time. Chemiluminescence is light produced from a chemical reaction without a rise in temperature. Luminol  BIOLUMINESCENCE The ability of a plant or animal to produce light Some algae, jellyfish, insects, crustaceans, bacteria, earthworms and fungi can produce light. All forms of bioluminescence are of chemiluminescence. Uses include: – Camouflage – Mimicry – Attracting mates – Distraction – Warning, communication, illumination Angler Fish  TRIBOLUMINESCENCE Triboluminescence is light produced from friction. Light is made through the breaking of chemical bonds when a material is pulled apart, ripped, scratched, crushed, or rubbed Some crystals such as quartz can be made to glow simply by rubbing them together or crushing them.  Light-emitting Diodes (LEDs) LEDs produce light from the movement of electrons in a piece of solid matter - specifically a semi-conductor. Semi-conductors consist of two components, one positive (has spaces for additional electrons) and one negative (has extra electrons). When an electric current reaches a semi-conductor, the extra electrons from the negative component move into the positive component spaces, which causes the production of light.