Producing Light: Incandescent & Fluorescent

Producing Light

• Incandescent light is produced by heating a piece of metal until it glows
• An incandescent light bulb contains a small wire coil called a filament, made of tungsten metal
• Electric current flows through the filament, the metal's resistance causes the filament to heat up and emit light

Fluorescent Lights

• Fluorescent light utilizes phosphors to convert ultraviolet radiation into visible light
• Emitting visible light occurs when phosphors absorb ultraviolet radiation

How Fluorescent Bulbs Work

• Fluorescent bulbs are filled with a gas at low pressure
• Electrodes at each end of the tube emit electrons when connected in a circuit
• Ultraviolet radiation is emitted when the electrons collide with the gas atoms
• Phosphors absorb the radiation and emit visible light

Efficient Lighting

• Fluorescent lights use significantly less electrical energy (as little as one fifth) to produce the same light compared to incandescent bulbs
• Fluorescent bulbs last longer than incandescent bulbs
• Higher efficiency can translate to lower energy costs over the lifespan of the bulb

Neon Lights

• Neon lights consist of glass tubes filled with gas, typically neon, and function similarly to fluorescent lights
• Visible light is produced when electrons collide with the gas molecules
• If the tube solely contains neon, the emitted light is bright red
• Different colors achieved by adding other gases to the tube

Sodium-Vapor Lights

• Sodium-vapor lamps contain a tube with a mixture of neon gas, a small amount of argon gas, and a small amount of sodium metal
• The gas mixture heats up when the lamp turns on
• The sodium metal turns to vapor from the hot gases
• Sodium vapor emits a yellow-orange glow

Tungsten-Halogen Lights

• These lights use a tungsten filament contained within a quartz bulb or tube
• The tube is filled with a gas containing a halogen, such as fluorine or chlorine

How Tungsten-Halogen Lights Work

• The tungsten filament becomes much hotter than in an ordinary incandescent bulb from the presence of halogen gas
• The light is brighter due because of the hotter filament
• The chemical interaction between the tungsten filament and the halogen gas extends the bulb's lifespan

Lasers

• Laser light emission begins with multiple light waves emitted simultaneously
• Identical atoms are needed to be given the same amount of energy to achieve the simultaneous light waves
• When atoms release their energy, each releases an identical light wave
• Some of this light wave is reflected between two facing mirrors at opposite ends

Lasers Details

• One of the mirrors is coated only partially with reflective material so light can escape
• Emitted light waves travel back and forth, prompting the other atoms to emit similar light waves
• Lasers use materials including including gases, liquids, and solids
• A red light beam is from a helium-neon laser

Coherent Light

• Light of only one wavelength
• light travels in one direction
• constant distance between corresponding crests.

Incoherent Light

• Light can contain more than one wavelength
• Electromagnetic waves are not aligned