Applied Science - Built Environment (5)
Lab

OBJECTIVES:

• Exploring how the light bulb changed our society.
• Comparing different light bulbs.

VOCABULARY:

• filament
• incandescent

MATERIALS:

• Bulbs (4 different types of bulbs) or
• Applied Science - Built Environment 5
• Swift GH microscope

Students look at filaments of different light bulbs under the microscope.

BACKGROUND:

Thomas Edison and many other inventors and scientists in the late 1800's, created and improved ways of capturing electricity to produce light. Ask students to imagine a world without the light bulb. It is almost unthinkable! Most students take the light produced by light bulbs for granted. Many do not even think about how marvelous this invention is.

During the lab, students will compare different parts of four different light bulbs. Students should especially look at the filament that generates "incandescence." Incandescence is the state of glowing at a high temperature. This is caused by electrons in vibrating atoms and molecules, which are moving in and out of their stable energy levels, and which emit radiation in the process. Radiation of many frequencies is emitted. (The electrons heat the filament causing it to "glow.") Students do not necessarily have to understand incandescent light or how filaments work. The key objective is for students to observe the filaments, which are key to how a bulb emits light.

A light bulb no longer emits light when the filament is finally "burned up!" This can be heard when you shake a burned out bulb. The sound you hear is the burned filament that has fallen to the base of the bulb.

Students may ask about fluorescent bulbs. Fluorescence works on a different principle than incandescence. A fluorescent lamp produces light by the passage of electricity through a vapor from a metal in a tube or bulb, which creates a glowing plasma. Fluorescent lamps do not have filaments.

The following is a list of filaments used during the development of the light bulb. The tungsten filament is the most commonly used today because it lasts longer than most other filaments. Research is still being conducted to created a better light bulb.

PROCEDURE:

1. During lab, students will look at the design of filaments. Put each bulb under the Swift GH and focus on the filament. Students should draw the different types of filaments on their lab sheet. The filament design helps the bulb last longer and utilizes the voltage more effectively. A simple bulb has a great deal of detail which may interest the students. Remember, the filament is in a vacuum. The vacuum is important because it allows the filament to burn slowly, increasing the life of the bulb. The filament is made first (by machine) and then put inside the bulb using vacuum technology. It is now automated, but imagine what it was like to make a light bulb by hand!
     
2. Have the students look at a light bulb that is on (not through the microscope), so they can observe that it is really the filament emitting light.