Refraction AP Physics 2 MCQ – Exam Style Questions etc.
Refraction AP Physics 2 MCQ
Unit 13: Geometric and Physical Optics
Weightage : 15–18%
Exam Style Practice Questions , Refraction AP Physics 2 MCQ
Questions
An absorption spectrum, observed for light traveling through interstellar gases, appears as a broad spectrum of light with isolated dark lines at frequencies characteristic of the molecules in the gases. Which of the following is primarily responsible for the location of the dark absorption lines in the spectrum?
(A) The characteristic velocities of the molecules in the gas
(B) The transition of electrons between discrete energy states within the gas molecules
(C) The percent of the gas molecules that were ionized by absorption of energy
(D) The fluctuations in density of molecules present in the interstellar gas cloud
▶️Answer/Explanation
Ans: B
This option is correct. The “location” of the dark lines is directly related to the color (and associated energy of that wavelength) of the light absorbed by the gas. This energy of this particular color is directly related to the transition of the electrons or the different “energy levels” in this particular gas.
Questions
A light ray enters a layer of water at point X, passes through a layer of glass, and exits through a layer of air at point Y, as shown in the figure above. Where would the ray exit the layer of air if the glass was replaced with a material of higher index of refraction?
(A) At a point above point Y
(B) At a point below point Y
(C) At point Y
(D) The location cannot be determined without knowing how much higher the index of refraction of the new material is.
▶️Answer/Explanation
Ans: A
This option is correct. By Snell’s law, a higher index of refraction results in a smaller angle of transmission; the ray in the middle layer is closer to horizontal. The ray hits the middle-layer/air boundary above the point shown in the figure. For that reason, and also because the angle of transmission into the air is less than before (because the angle of incidence is less), the ray exits the air layer above point Y.
Question
A ray of light in air (n = 1.0) is incident on glass (n = 1.5) at a small angle \(\theta _{a}\) to the normal. The angle of the ray to the normal in the glass is \(\theta _{g}\) . The speeds of light in air and the glass are \(v _{a}\) and \(v _{g}\) , respectively. How do the values of the speed of light and the angle of the ray of light to the normal in air compare to those in the glass?
Speed of Light Angle to Normal
(A) \(v _{a}\) > \(v _{g}\) \(\theta _{a}\) > \(\theta _{g}\)
(B) \(v _{a}\) > \(v _{g}\) \(\theta _{a}\) < \(\theta _{g}\)
(C) \(v _{a}\) < \(v _{g}\) \(\theta _{a}\) > \(\theta _{g}\)
(D) \(v _{a}\) < \(v _{g}\) \(\theta _{a}\) < \(\theta _{g}\)
Answer/Explanation
Ans:A
Question
On a calm day, student 1 looks down into a pool and sees student 2 swimming underwater. At the same time, student 2 looks up from under the water and sees student 1. In the following diagrams, the oval represents student 1 and the rectangle represents student 2. Diagrams that correctly illustrate the apparent positions seen by student 1 and student 2 include which of the following? Select two answers.
Answer/Explanation
Ans:A, C
Question
Light from inside an aquarium filled with water strikes the glass wall as shown in the figure. Knowing that nwater = 1.33 and nglass = 1.62, which of the following represents a possible path that the light could take?
Answer/Explanation
Ans:
C-Light traveling from the water to the glass should bend toward the normal as it slows down in the glass. This eliminates answer choices B and D. The light will then travel from the glass to the air on the left where it will bend away from the normal because it is traveling fastest in the air. Answer choice A seems to show the angle in the air being the same as it was in the water, which cannot be true. The light travels faster in air than in water, which means the angle to the normal must be bigger than inside the aquarium. What about answer choice C? Since the light bends away from the normal entering air, it is possible that the angle of incidence between the glass and the air is beyond the critical angle, thus causing total internal reflection at the glass/air boundary; C is the best answer.