A bell jar is a piece of laboratory glassware in the shape of a bell. It can be sealed, which allows it to be used in a classroom science experiment involving an alarm clock and a vacuum pump. The air is pumped out of the sealed bell jar, and the noise of the alarm clock fades, thus proving that sound travels through vibrations in matter, not as waves. Jump to: navigation, search Laboratory glassware refers to a variety of equipment, traditionally made of glass, used for scientific experiments in chemistry and biology. ... Jump to: navigation, search Bell may refer to: Look up bell on Wiktionary, the free dictionary. ... Jump to: navigation, search From Latin ex- + -periri (akin to periculum attempt). ... A wind-up alarm clock An alarm clock is a clock that is designed to make an alarm sound at a specific time. ... Jump to: navigation, search For other uses, see vacuum cleaner and Vacuum (musical group). ... Jump to: navigation, search A schematic representation of hearing. ... See Oscillator (disambiguation) for particular types of oscillation and oscillators. ... Jump to: navigation, search A wave is a disturbance that propagates in a periodically repeating fashion, often transferring energy. ...