Test: ACT Science

A fiber-optic Michelson interferometer is a device that detects changes in optical paths. In a fiber-optic interferometer, a coherent light source (usually a laser) is sent through a beam splitter that splits the light along two paths. These beams are coupled into fiber optic cables that can be arranged and manipulated more freely than mirrors. The two beams are finally recombined by a second beam splitter and superimposed on a screen. If there is a phase difference between the two waves, interference fringes will be viewed on the screen.


By observing fringe shifts, one can quantify the change in optical path difference between the two fibers using the following equation:

where m is the number of fringe shifts, x is the difference between the optical paths of the two beams, and  is the change in the optical path difference.

Experiment 1:

A student sets up a fiber-optic Michelson interferometer and heats one of the fibers with various resistors and power supplies, fans air over one of the fibers, and then bends one of the fibers. The resulting fringe shifts, as well as the change in optical path difference (OPD), are shown below.




One way optical fibers can contract and expand is through thermal changes. According to the data, what is the effect of increasing the voltage drop through a resistor?

The increased voltage leads to a greater decrease in the speed of light.

The increased voltage allows for more efficient electric transmission.

The increased voltage leads to higher power dissipation.

The increased voltage does not affect the experimental data.

1/11 questions


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