An experiment with light rays and a prism
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- An experiment with light rays and a prism
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An experiment with light rays and a prism
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[post_date] => 2025-01-09 11:16:03
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[post_content] => Practice Passage (Question 1-5)
*This passage is the property of Khan Academy and has been reformatted into an AAMC-style interface in their entirety by MedLife Mastery. MedLife Mastery does not endorse and is not an affiliate of Khan Academy.
A student is conducting an experiment to explore the angles made by reflected and refracted light. To do this the student uses a laser to fire a ray of light toward a rectangular prism that has an index of refraction of np. The laser light first strikes the surface of the prism at an angle θ1. Some of the light is reflected off of the front diagonal surface of the prism. The rest of the light is refracted through the prism at an angle θ3. This refracted light makes its way to the backside of the prism at an angle θ4 and is refracted once more from the prism into the air at an angle of θ5. This process is represented in the diagram below. Dotted lines are not part of the experiment and are shown in the diagram for reference purposes only. The right angle symbol is used to represent angles of 90°. Angles shown in the diagram are not necessarily drawn exactly to proportion.
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[questions] => Array
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[quiz_unique_key] => 578908434
[question] => What is the value of angle θ2?
[value] => Array
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[answer] => 3
[description] => Reason for the Correct Answer:
The law of reflection says the angle in equals the angle out
Careful, θ2 is not measured with respect to the normal line
The angle of the reflected ray measured from the normal line is 55°, so the angle θ2 =35°, to ensure they add up to 90°.
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[answers] => Array
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[0] => Array
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[each_answer] => A. 2θ1
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[1] => Array
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[each_answer] => B. θ1
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[2] => Array
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[each_answer] => C. 90° – θ1
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[3] => Array
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[each_answer] => D. 90 + θ1
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[1] => Array
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[quiz_unique_key] => 3873426850
[question] => What is the value of angle θ3?
[value] => Array
(
[answer] => 2
[description] => Reason for the Correct Answer:
Use Snell’s Law
Remember to measure all angles from the normal line
n1sinθ1 = n2sinθ2 which after substituting gives 1sin(sinθ1 = npsinθ3 and after solving gives θ3= sin-1 (sinθ1/np).
)
[answers] => Array
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[0] => Array
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[each_answer] => A. sin (sinθ1/np)
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[1] => Array
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[each_answer] => B. sin-1 (sinθ1/np)
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[2] => Array
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[each_answer] => C. sin-1 (np/sinθ1)
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[3] => Array
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[each_answer] => D. sin (np/sinθ1)
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[2] => Array
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[quiz_unique_key] => 83407773
[question] => What is the value of angle θ5?
[value] => Array
(
[answer] => 2
[description] => Reason for the Correct Answer:
Use Snell’s Law
Remember to measure all angles from the normal line
The angle in the prism from the normal line is 90 – θ4
n1sinθ1 = n2sinθ2 which after substituting gives np(90-θ4)=1sinθ5 and after solving gives θ5=sin-1[npsin(90-θ4)]
)
[answers] => Array
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[0] => Array
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[each_answer] => A. sin(np*sin(90-θ4)
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[1] => Array
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[each_answer] => B. sin-1[np*sin(90-θ4)]
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[2] => Array
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[each_answer] => C. 90 – sin-1[np*sinθ4]
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[3] => Array
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[each_answer] => D. sin-1[90-np*sinθ4]
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[3] => Array
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[quiz_unique_key] => 2261298308
[question] => The student now wants to change the lab set up to observe a total internal reflection event. Which of the following would increase the likelihood of seeing a total internal reflection event?
[value] => Array
(
[answer] => 2
[description] => Reason for the Correct Answer:
Total internal reflection only happens when light would refract into a faster material
Total internal reflection first happens when the refracted angle is 90°
To get total internal reflection you need θ5 to increase and approach 90°
The only choice given that will increase the refracted angle θ5 is to decrease θ4
)
[answers] => Array
(
[0] => Array
(
[each_answer] => A. Increase θ1
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[1] => Array
(
[each_answer] => B. Decrease θ4
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[2] => Array
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[each_answer] => C. Decrease θ5
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[3] => Array
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[each_answer] => D. Increase θ3
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[4] => Array
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[quiz_unique_key] => 2377279144
[question] => Which of the following expressions is equal to the critical angle required for observing a total internal reflection event using this prism surrounded by air?
[value] => Array
(
[answer] => 3
[description] => Reason for the Correct Answer:
Total internal reflection first happens when the refracted angle is 90°
Use Snell’s Law with and set the refracted angle equal to 90°
n1sinθ1 = n2sinθ2 which after substituting gives npsin(θc)=1sin90, and after solving gives θc=sin-1(1/np)
)
[answers] => Array
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[0] => Array
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[each_answer] => A. sin-1(np-90)
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[1] => Array
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[each_answer] => B. sin-1(90-np)
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[2] => Array
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[each_answer] => C. sin-1(1/np)
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[3] => Array
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[each_answer] => D. sin-1(np)
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[559827|5] => C
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