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A student wants to scale down Michelson\'s light-speed experiment to a size that

ID: 1792142 • Letter: A

Question

A student wants to scale down Michelson's light-speed experiment to a size that will fit in one room. A six-sided mirror is available, and the stationary mirror can be mounted 11.1 m from the rotating mirror. If the arrangement is otherwise as shown in the figure below, at what minimum rate must the mirror rotate?

A student wants to scale down Michelson's light-speed experiment to a size that wl fit in one room. A six-sided mirror is available, and the stationary mirror can be mounted 11.1 m trom the rotating mirror. It the arrangement is otherwise as shown in the figure below, at what minimum rate must the mirror rotate? 1.4e7 Observer Stationary Eight-sided rotating mirror Light M.. Wilson) Mt. Baldy 35 km

Explanation / Answer

The light is emitted by a source S , reflected off an orthogal mirror A and travels to a 2nd mirror . When it comes back it is, once again, bounced off the rotating mirror C and seen by the observer. While the light travels, the mirror B moved to C. The time required for B to move to C was just one eighth of the timed needed for one revolution of the mirror. Starting from rest, the speed of the motor was adjusted until the light reflected from C was clearly observed through the telescope.

The total distance the light travels is 2 * 11.1 m = 22.2m
the time taken for light to travel this distance is t = 22.2 / 299 792 458 m / s

t = 22.2m / 299. 792 458 m / us = 0.074 us

time for 1 rotation = 8 * 0.074 us = 0.592 us

rotational speed = 1.688 * 10^6 rotations per second

or 1.06 * 10^7 rad/s