AP Physics 2 Unit 13 practice questions
Try 10 multiple-choice questions from Unit 13 here. Pick an answer to see why it's right or wrong, then take the timed test above for a full AP-style set.
Question 1
A laser beam strikes a plane mirror, making an angle of 35° with the surface of the mirror. Based on the law of reflection, what is the angle between the incident beam and the reflected beam?
70°, since the angle of incidence is 35°
110°, since the angle of incidence is 55°
55°, since the angle of reflection is 55°
35°, since the angle of reflection is 35°
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Answer: (B)
Calculating the angle of incidence as 90° - 35° = 55° allows for the correct application of the law of reflection. Since the angle of reflection equals the angle of incidence (55°), the total angle between the rays is 55° + 55° = 110°.
Question 2
A student observes that a polished metal sheet forms a clear image, but a piece of white paper does not, even though both reflect light. Which statement best applies the ray model of light to explain this difference?
The paper absorbs most light rays, while the metal reflects them
The paper reflects rays in random directions due to surface roughness
The paper transmits light rays, while the metal blocks their passage
The paper changes the frequency of light rays upon reflection
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Answer: (B)
Applying the concept of diffuse reflection explains why rough surfaces do not form images. While the law of reflection holds locally for each ray, the varying surface normals cause parallel incident rays to scatter in many directions.
Question 3
A point source emits light waves in all directions. How does the ray model describe the relationship between the light rays and the wavefronts propagating from this source?
Rays are parallel to the wavefronts and indicate energy flow
Rays are perpendicular to the wavefronts and point radially outward
Rays are parallel to the wavefronts and point radially inward
Rays are perpendicular to the wavefronts and indicate wave speed
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Answer: (B)
Describing light as a ray involves recognizing that rays represent the direction of energy propagation. Rays are always constructed perpendicular to the wavefronts, pointing away from the source.
Question 4
Two plane mirrors are joined at a 90° angle. A light ray strikes the first mirror with an angle of incidence of 40° and reflects toward the second mirror. What is the angle of reflection at the second mirror?
40°, because the angle of incidence is conserved
50°, because the normal lines are perpendicular
80°, because the total reflection angle doubles
100°, because the ray reflects back to the source
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Answer: (B)
Applying the law of reflection and geometry reveals the new angle. The ray reflects off the first mirror at 40°, making a 50° angle with the first surface. Since the mirrors are perpendicular, the ray makes a 40° angle with the second surface, resulting in a 50° angle of incidence and reflection.
Question 5
A laser beam strikes a plane mirror at a fixed angle. If the mirror is rotated by an angle about an axis in the plane of the mirror, by what angle does the reflected ray deviate from its original path?
It deviates by an angle equal to
It deviates by an angle equal to
It deviates by an angle equal to
It deviates by an angle equal to
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Answer: (B)
Rotating the mirror by rotates the normal line by . This increases the angle of incidence by and the angle of reflection by , resulting in a total change of for the reflected ray.
Question 6
At night, a driver finds that dry pavement is illuminated evenly by headlights, but wet pavement creates a blinding glare from oncoming lights. Which claim correctly applies the model of reflection to explain this?
Water absorbs light rays, reducing the total reflected intensity
Water fills surface crevices, causing specular reflection of rays
Water scatters light rays, increasing the diffuse reflection angle
Water refracts light rays, bending them away from the driver's eyes
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Answer: (B)
Applying the concept of surface smoothness explains the glare. Water fills the rough texture of the asphalt, creating a smooth surface that supports specular reflection, directing light rays intensely toward the driver.
Question 7
A student uses the ray model to predict the behavior of light passing through a narrow slit. Under which condition would the ray model fail to accurately predict the resulting pattern on a screen?
When the slit width is much larger than the light's wavelength
When the slit width is comparable to the light's wavelength
When the light intensity is high enough to heat the slit edges
When the distance to the screen is small relative to the slit
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Answer: (B)
Identifying the limits of the ray model is key. When the aperture size approaches the wavelength of light, diffraction effects become significant, and the wave model is required.
Question 8
An object is placed 0.5 m in front of a plane mirror. Based on the law of reflection and ray tracing, which statement correctly describes the image formed?
The image is real and located 0.5 m behind the mirror surface
The image is virtual and located 0.5 m behind the mirror surface
The image is real and located 0.5 m in front of the mirror surface
The image is virtual and located 0.5 m in front of the mirror surface
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Answer: (B)
Ray tracing for a plane mirror shows that reflected rays diverge. Extending them backward creates a virtual image located equidistant from the mirror as the object.
Question 9
A red apple is illuminated by a white light source. A student can see the apple from any position in the room. Which process best explains this observation using the ray model?
Specular reflection sends parallel rays to all observers
Diffuse reflection scatters rays in multiple directions
Refraction bends rays around the curvature of the apple
Diffraction spreads rays as they reflect off the surface
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Answer: (B)
Applying the concept of diffuse reflection explains the visibility. The rough surface of the apple scatters incident light rays in all directions, allowing observers at various locations to intercept them.
Question 10
A physicist models a laser beam as a single ray of light. For which of the following interactions is this approximation most valid?
The beam reflecting off a flat mirror surface
The beam passing through a diffraction grating
The beam passing through a double-slit apparatus
The beam passing through a microscopic aperture
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Answer: (A)
Geometric optics (the ray model) is valid here. Reflection off a macroscopic mirror does not induce significant wave effects like diffraction, so the single ray approximation holds.
What's on the AP Physics 2 Unit 13 practice test
The standard version takes about 88 minutes and follows the timing and directions of the AP exam, sized to one unit:
- 20 Multiple Choice Questions (40 minutes)
- 1 FRQ – FRQ 1 – Mathematical Routines (24 minutes)
- 1 FRQ – FRQ 2 – Translation Between Representations (24 minutes)
Questions are drawn from 648 multiple-choice questions and 33 FRQs written for Unit 13, Geometric Optics.
Practice AP Physics 2 Unit 13 FRQs
Answer the unit's free-response questions one at a time and get a score on every part.
- FRQ 1 – Mathematical Routines (9 questions)
- FRQ 2 – Translation Between Representations (9 questions)
- FRQ 3 – Experimental Design (2 questions)
- FRQ 4 – Qualitative/Quantitative Translation (13 questions)