An academic competition challenges students to design an experiment that clearly distinguishes whether a wave needs a material medium in order to propagate. The only available equipment includes:
• A bell that produces audible sound
• A battery-powered light-emitting diode (LED)
• A bell jar connected to a vacuum pump with an analog pressure gauge
• Standard timing devices and meters
• Materials for wiring and supports
You have been asked to propose and justify a complete experimental procedure that meets the challenge using only the items above.
(a) Outline a step-by-step experimental procedure, including any measurements to be taken, that would allow observers to determine whether the bell’s sound and the LED’s light require a material medium to reach a detector located outside the bell jar.
(b) Describe the expected qualitative observations for both the sound from the bell and the light from the LED as the air pressure inside the bell jar is gradually reduced toward near-vacuum.
(c) Explain how the observations constitute evidence regarding the necessity of a medium for each type of wave.
(d) Identify two potential sources of experimental error or ambiguity in the proposed procedure and suggest methods to mitigate them.