Question

Typing The Answer Is Mandatory

Examine the structures of the bulbs to form a conclusion as to the reason that fluorescent bulbs last longer than incandescent bulbs.

Answer 1

When an incandescent bulb is hooked up to a power supply, the electric current passes through a metal filament (usually tungsten), heating it until the filament is so hot that it glows. As the electrons move, they bump into the metal atoms of the filament. The energy of each collision vibrates the atoms and heats them up, eventually producing light. Only 10% of the energy used by an incandescent bulb is converted to light; the other 90% is lost as heat. The tray model represents the collisions between the electrons and the atoms of the filament.

In a fluorescent bulb, rather than passing through a filament, the electric current flows through a glass tube that is filled with mercury gas and coated on the inside with a phosphor coating. When electrons collide with the mercury atoms, the mercury atoms are excited to produce an invisible ultraviolet light. The phosphor coating then absorbs energy from the ultraviolet light and fluoresces, or turns the invisible light into visible light. In fluorescent light bulbs, the light is created by high-energy dislodged electrons that are produced when electric current is applied to the mercury gas; heat is created as a byproduct of these energetic electrons. About 85% of the energy used by a fluorescent bulb is converted to light. The tray model represents the collisions between the electrons and the mercury atoms.

The LED bulb contains a number of different light emitting diodes, each of which produces light from a semiconductor chip with a negatively charged terminal and a positively charged terminal. As electrons move from negative to positive, they collide with positively charged particles (“holes”) and fall from a high energy level to a lower energy level. The drop releases energy in the form of light.

Since LEDs use electricity more efficiently than the other two types of bulbs (they convert about 90% of it to light), they require much less energy to produce the same amount of light as incandescent or fluorescent bulbs. The tray model represents the collisions between the electrons and the holes. Since the type of collision differs in each type of bulb, trying to compare them may seem like comparing apples and oranges. The simplest way to think about the comparison is to consider that no matter what kind of bulb, there are electrons involved in collisions that produce light or heat. Roughly speaking, the ratio of light-producing collisions to heat-producing collisions in each bulb explains its efficiency.