Ch 18-5 Sources of Light

Objects that give off their own light are LUMINOUS

Incandescent Light

• Light produced when a object gets hot enough to glow

• Electrons flow throw a filament in the bulb, when it gets hot it emits light.

Fluorescent Light

• Emits light by causing a phosphor to steadily emit photons.

• Essentially is it a string of collisions changing wave lengths into visible light.

• More energy efficient than incandescent bulb

Laser Light

• Laser is a beam of coherent light

• It is emitted when excited atoms emit photons.

• Coherent light does not spread out so it has a constant intensity.

• Can be used to cut, heat materials. Carry information or make measurements.

Neon Light• Neon lights emit light when electrons move

through a gas or a mixture of gases in glass tubing.

• Different gases or mixtures give off different light colors.

Sodium-Vapor Light

• As electric current passes through a sodium-vapor bulb it ionizes the gas mixtures. As the mixture warms up it’s heats causes the sodium to change from solid into a gas.

• The move electrons into higher energy levels, when the electrons return to the lower energy they release energy.

• Very energy efficient and very bright.• Often used as parking lot and street lights.

Other Lights

• Tungsten-Halogen light - like an incandescent light but uses a tungsten filament and last longer than incandescent.

• LED – Light Emitting Diode – they have a low energy consumption, often many are used together to produce a bright light.