MCAT Physical : Polarization

Study concepts, example questions & explanations for MCAT Physical

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Example Questions

Example Question #1 : Polarization

Unpolarized light passes through three polarizing filters. The angle between the first and second filters is 45o. The angle between the second and third filters is also 45o. What is the relationship between the intensity of light emerging from the third filter, , and the incident intensity,  ?

Possible Answers:

No light passes through the third filter

Correct answer:

Explanation:

Going through the first filter, the intensity of initially unpolarized light decreases by 1/2, so . For each filter after the first, the intensity decreases by an additional factor of , where  is the angle between adjacent polarizers. So, after the second filter, we have can see that . Similarly, after the third filter, we have .

Example Question #2 : Polarization

Unpolarized monochromatic light passes through a single polaroid filter, oriented horizontally. It then encounters a second filter that is oriented vertically. Which of the following statements is true of the resulting light?

Possible Answers:

The emerging light has the same intensity, but is now polarized at

The emerging light has one-fourth the incident intensity and is polarized vertically

The light is entirely blocked

The emerging light has one half of the incident intensity and is polarized vertically

The emerging light has one half the incident intensity and is polarized at

Correct answer:

The light is entirely blocked

Explanation:

The first filter polarizes the light horizontally, only allowing light to pass if it is oscillating horizontally. This would decrease the intensity by one-half.

The second filter would polarize the light vertically, only allowing light to pass if it oscillates vertically. The first filter, however, has already blocked all non-horizontal waves, including any vertical waves; thus, there are no remaining waves that can pass through the vertical filter. The light is fully blocked by this combination.

Example Question #3 : Polarization

Each of the following types of waves experience polarization except __________.

Possible Answers:

sound waves

electromagnetic waves

transverse waves

light waves

Correct answer:

sound waves

Explanation:

Polarization is the property that allows tansverse waves to oscillate in multiple orientations. A transverse wave can oscillate, for example, in either the xy-plane or the yz-plane.

Sound waves are longitudinal, and thus do no experience polarization as medium is displaced in one direction only. A longitudinal wave will travel in only one dimension via compression and rarefraction.

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