AP Physics 2 Quiz: Refraction

20 questions · exam conditions

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RefractionQuestion 1 of 20

A light ray travels in glycerin and reaches a boundary with water at $45^\circ$ to the normal. Glycerin has the higher refractive index ( $n_{glycerin} > n_{water}$ ). Which way does the ray bend as it enters the water?

Toward the normal in water

Away from the normal in water

Toward the normal because the speed increases

Away from the normal because the frequency increases

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AP Physics 2 Quiz

AP Physics 2 Quiz: Refraction

Practice Refraction in AP Physics 2 with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Refraction, giving you a quick way to practice the rules, question types, and explanations that matter most for AP Physics 2.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

Toward the normal in water
Away from the normal in water (correct answer)
Toward the normal because the speed increases
Away from the normal because the frequency increases

Explanation: This question involves refraction. When light travels from glycerin (higher refractive index) to water (lower refractive index), the light wave speeds up as it enters the less dense medium. This increase in speed at the boundary causes the light ray to bend away from the normal. The refracted ray in water makes a larger angle with the normal than the 45° incident angle in glycerin. Choice C incorrectly states the ray bends toward the normal because speed increases, confusing both the bending direction and misunderstanding that speed actually increases when entering a less dense medium. Apply this principle: light entering a less dense medium (lower n) speeds up and bends away from the normal.

Question 2

A monochromatic light ray in air enters ethanol at an incident angle of $15^\circ$ to the normal. Ethanol has the higher refractive index ( $n_{ethanol} > n_{air}$ ). Which way does the ray bend upon entering ethanol?

Away from the normal in ethanol
Toward the normal in ethanol (correct answer)
Away from the normal because the speed decreases
Toward the normal because the frequency changes

Explanation: This problem tests refraction. When light enters ethanol from air, it moves from a medium with lower refractive index to one with higher refractive index, causing the light wave to slow down. This speed reduction at the boundary makes the light ray bend toward the normal. Even with a small incident angle of 15°, the refracted ray still bends toward the normal, just with a smaller refraction angle. Choice D incorrectly attributes the bending to frequency change, revealing the misconception that frequency varies during refraction when it actually stays constant. The fundamental rule: light entering a denser medium (higher n) slows down and bends toward the normal.

Question 3

A beam travels in air and enters water at $35^\circ$ to the normal. Water has the higher refractive index ( $n_{water} > n_{air}$ ). Which option correctly describes the refraction direction at the boundary?

It bends away from the normal in water
It bends toward the normal in water (correct answer)
It bends away from the normal because the speed decreases
It bends toward the normal because the frequency increases

Explanation: This problem addresses refraction. When light travels from air (lower refractive index) to water (higher refractive index), the light wave slows down as it enters the denser medium. This speed reduction at the boundary causes the light ray to bend toward the normal. The refracted ray in water makes a smaller angle with the normal than the 35° incident angle. Choice C incorrectly states the ray bends away from the normal because speed decreases, revealing confusion about the relationship between speed change and bending direction. To predict refraction: when light enters a denser medium (higher n), it slows down and bends toward the normal.

Question 4

A light ray travels in a high-index crystal and enters air at $10^\circ$ to the normal. The crystal has the higher refractive index ( $n_{crystal} > n_{air}$ ). Which way does the ray bend as it enters air?

Away from the normal in air (correct answer)
Toward the normal in air
Toward the normal because the speed increases
Away from the normal because the frequency decreases

Explanation: This question tests refraction. When light exits a high-index crystal and enters air (lower refractive index), the light wave speeds up in the less dense medium. This speed increase at the boundary causes the light ray to bend away from the normal. Even with a small incident angle of 10°, the refracted ray still bends away from the normal, just with a proportionally small increase in angle. Choice D incorrectly suggests frequency decreases, demonstrating the misconception that frequency changes during refraction when it remains constant throughout. The key insight: light exiting a denser medium (higher n) speeds up and bends away from the normal.

Question 5

A laser beam travels in a plastic slab and exits into air at a flat boundary. The plastic has a higher refractive index than air. For a nonzero incident angle, compared to the incident ray, the refracted ray in air bends which way?

Toward the normal, because the speed decreases in air
Away from the normal, because the speed increases in air (correct answer)
Toward the normal, because the frequency changes at the boundary
Away from the normal, because the frequency increases in air

Explanation: This question tests understanding of refraction. When light travels from plastic (higher refractive index) to air (lower refractive index), the light speed increases. As wave fronts cross into air, they speed up, causing the ray to bend away from the normal—like a car wheel leaving sand onto pavement at an angle. Choice D incorrectly claims frequency increases in air, revealing the misconception that frequency changes at boundaries when it actually remains constant. Remember: when light enters a less dense medium, it speeds up and bends away from the normal.

Question 6

A laser beam travels in glass and reaches a flat glass–air boundary at $20^\circ$ to the normal. Glass has a higher refractive index than air. Neglect reflection. Compared to the incident ray, the refracted ray in air bends which way?

Toward the normal, because the speed increases in air
Away from the normal, because the speed increases in air (correct answer)
Toward the normal, because the frequency decreases in air
Away from the normal, because the wavelength must stay constant

Explanation: This question tests understanding of refraction. When light travels from a medium with higher refractive index (glass) to one with lower refractive index (air), the light speed increases. As the wave fronts cross the boundary, those entering air first travel faster than those still in glass, causing the ray to bend away from the normal. Choice D incorrectly claims wavelength stays constant—wavelength actually increases in air while frequency remains constant, revealing the misconception that wavelength is conserved across boundaries. Remember: when light enters a less dense medium (lower n), it bends away from the normal.

Question 7

A narrow light ray in air strikes a flat boundary with glass at an incident angle of $40^\circ$ measured from the normal. The glass has a higher refractive index than air ( $n_{glass} > n_{air}$ ). Ignoring reflection, the ray enters the glass at the point of incidence. Which way does the ray bend as it crosses into the glass?

It bends toward the normal because the speed decreases. (correct answer)
It bends toward the normal because the frequency increases.
It bends away from the normal because the speed increases.
It continues straight because the frequency must stay constant.

Explanation: This question tests understanding of refraction. When light travels from a medium with lower refractive index (air) to one with higher refractive index (glass), the light speed decreases because v = c/n, where n is the refractive index. At the boundary, the component of the wave's velocity parallel to the surface must remain continuous, while the perpendicular component changes due to the speed change. This causes the light ray to bend toward the normal (the line perpendicular to the surface) when entering a denser medium. Choice C incorrectly assumes that constant frequency prevents bending, but frequency conservation doesn't determine ray direction—the speed change does. When light slows down entering a denser medium, always remember it bends toward the normal.

Question 8

A laser beam travels in water and strikes a water–air boundary at $25^\circ$ to the normal. Air has the lower refractive index ( $n_{water} > n_{air}$ ). The beam transmits into the air. Compared to the incident ray, the refracted ray in air is at a(n) angle to the normal.

smaller angle because the speed decreases
smaller angle because the frequency increases
larger angle because the speed increases (correct answer)
unchanged angle because the wavelength stays constant

Explanation: This question tests understanding of refraction. When light travels from a medium with higher refractive index (water) to one with lower refractive index (air), the light speed increases according to $v = c/n$ . As the wave crosses the boundary, the parallel component of velocity remains constant while the perpendicular component increases, causing the ray to bend away from the normal. Since the light speeds up in air, the refracted angle becomes larger than the incident angle of $25^\circ$ . Choice B incorrectly claims frequency increases, but frequency remains constant across boundaries—only speed and wavelength change. When light speeds up entering a less dense medium, it always bends away from the normal.

Question 9

A ray of light travels from crown glass into air at a flat interface. Crown glass has higher refractive index than air ( $n_{glass} > n_{air}$ ). The ray refracts into the air. Which way does the refracted ray bend relative to the normal?

Toward the normal because the speed decreases
Away from the normal because the speed decreases
Away from the normal because the speed increases (correct answer)
Toward the normal because the frequency increases

Explanation: This question tests understanding of refraction. When light travels from crown glass (higher refractive index) to air (lower refractive index), the wave speed increases since v = c/n and n_air < n_glass. As the wavefront crosses the boundary, the portion entering air first speeds up relative to the part still in glass, causing the wavefront to rotate away from the normal line. This bending away from the normal always happens when light enters a less dense optical medium. Choice A incorrectly states the speed decreases, showing the misconception that light always slows down at boundaries—actually, speed change depends on relative refractive indices. Remember: when light speeds up (entering lower n media), it bends away from the normal.

Question 10

A monochromatic beam travels from ethanol into acrylic at an incident angle of $50^\circ$ to the normal. Acrylic has the higher refractive index ( $n_{acrylic} > n_{ethanol}$ ). The ray enters the acrylic. Which way does the ray bend at the boundary?

Away from the normal because the speed decreases
Toward the normal because the speed decreases (correct answer)
Away from the normal because the frequency decreases
Toward the normal because the wavelength stays constant

Explanation: This question tests understanding of refraction. When light travels from ethanol (lower refractive index) to acrylic (higher refractive index), the wave speed decreases since v = c/n and n_acrylic > n_ethanol. At the boundary, the leading edge of the wavefront enters the acrylic and slows down while the trailing edge continues at ethanol speed, causing the wavefront to rotate toward the normal. This bending toward the normal characterizes light entering a denser optical medium. Choice D incorrectly claims wavelength stays constant, revealing the misconception that wavelength is preserved during refraction—actually, wavelength changes proportionally with speed while frequency remains constant. Remember: waves bend toward the normal when entering a medium where they slow down.

Question 11

A light ray goes from air into a transparent liquid at $30^\circ$ to the normal. The liquid has higher refractive index than air ( $n_{liquid} > n_{air}$ ). The ray enters the liquid. Compared to the incident ray, the refracted ray bends which way?

Toward the normal because the speed decreases (correct answer)
Away from the normal because the speed increases
Toward the normal because the frequency increases
Away from the normal because the wavelength stays constant

Explanation: This question tests understanding of refraction. When light goes from air (lower refractive index) into a liquid (higher refractive index), the wave speed decreases because v = c/n, where n_liquid > n_air. At the boundary, the leading edge of the wavefront enters the liquid and slows down while the trailing portion continues at air speed, causing the wavefront to pivot toward the normal. This bending toward the normal characterizes light entering a denser optical medium. Choice D incorrectly claims wavelength stays constant, revealing the misconception that wavelength is preserved during refraction—wavelength actually changes with speed (λ = v/f) while frequency remains constant. Remember: waves bend toward the normal when they slow down (entering higher n media).

Question 12

A light ray in glass approaches a boundary with water at $35^\circ$ to the normal and refracts into the water. Glass has higher refractive index than water ( $n_{glass} > n_{water}$ ). Compared to the incident ray, which way does the refracted ray bend?

Toward the normal because the speed decreases
Away from the normal because the speed increases (correct answer)
Toward the normal because the frequency decreases
Away from the normal because the frequency increases

Explanation: This question tests understanding of refraction. When light travels from glass (higher refractive index) to water (lower refractive index), the wave speed increases because v = c/n, and n_water < n_glass. As the wavefront crosses the boundary, the part entering water first speeds up relative to the portion still in glass, causing the wavefront to pivot away from the normal. This bending away from the normal always happens when light enters a less dense optical medium. Choice C incorrectly states frequency decreases, showing the misconception that frequency changes at boundaries—frequency is set by the source and never changes during refraction. Remember: when light speeds up (going from higher to lower n), it bends away from the normal.

Question 13

A monochromatic light ray travels in water and enters a layer of mineral oil at $30^\circ$ to the normal. Water has the higher refractive index ( $n_{\text{water}} > n_{\text{oil}}$ ). As the ray enters the oil, which way does it bend?

Away from the normal, because the speed increases in oil (correct answer)
Toward the normal, because the frequency decreases in oil
Away from the normal, because the frequency increases in oil
Toward the normal, because the speed increases in oil

Explanation: This question tests understanding of refraction. When light travels from water (higher refractive index) to mineral oil (lower refractive index), the light speed increases because v = c/n, where oil's lower n means higher speed. At the water-oil boundary, the parallel component of the wave maintains continuity, but the overall speed increase causes the ray to bend away from the normal. This follows Snell's law: n₁sin(θ₁) = n₂sin(θ₂), where oil's smaller n₂ results in a larger angle θ₂ from the normal. Choice C incorrectly claims frequency increases, but frequency is determined by the source and remains constant during refraction. The transferable principle is: when light speeds up (entering a less dense medium), it always bends away from the normal.

Question 14

A ray of light in air enters a liquid with $n=1.60$ at $45^\circ$ to the normal. The liquid has the higher refractive index ( $n_{\text{liquid}} > n_{\text{air}}$ ). Compared to the incident ray, how does the transmitted ray bend?

Toward the normal, because the frequency increases in the liquid
Away from the normal, because the speed decreases in the liquid
Toward the normal, because the speed decreases in the liquid (correct answer)
Away from the normal, because the frequency decreases in the liquid

Explanation: This question tests understanding of refraction. When light travels from air (n ≈ 1.0) to a liquid with n = 1.60, the light speed decreases significantly because v = c/n. At the air-liquid boundary, the wave's parallel component must maintain continuity, but the overall speed reduction causes the ray to bend toward the normal. This is quantified by Snell's law: n₁sin(θ₁) = n₂sin(θ₂), where the liquid's larger n₂ = 1.60 requires a much smaller refraction angle θ₂. Choice C incorrectly suggests frequency increases, but frequency is an intrinsic property of the light source that never changes during refraction. The key strategy is: waves bend toward the normal when they slow down (entering a denser medium).

Question 15

A narrow light ray in air strikes a flat boundary to glass at an incident angle of $40^\circ$ to the normal. The glass has a higher refractive index than air ( $n_{glass} > n_{air}$ ). Assume the boundary is smooth and the ray enters the glass. Which way does the ray bend as it refracts into the glass?

Toward the normal because the frequency increases
Toward the normal because the speed decreases (correct answer)
Away from the normal because the speed increases
Away from the normal because the wavelength decreases

Explanation: This question tests understanding of refraction. When light travels from a medium with lower refractive index (air) to one with higher refractive index (glass), the wave speed decreases because v = c/n, where n is the refractive index. At the boundary, the side of the wavefront that enters the glass first slows down while the other side continues at the original speed, causing the wavefront to pivot toward the normal. This bending toward the normal occurs whenever light enters a denser optical medium. Choice C incorrectly states that frequency increases, revealing the misconception that frequency changes during refraction—frequency actually remains constant as it depends only on the source. Remember: when light slows down (entering a higher n medium), it bends toward the normal.

Question 16

A light ray in air enters a transparent liquid at a flat surface. The liquid has a higher refractive index than air. If the incident angle is not $0^\circ$ , which way does the transmitted ray bend in the liquid?

Toward the normal, because the speed decreases in the liquid (correct answer)
Away from the normal, because the speed decreases in the liquid
Toward the normal, because the frequency increases in the liquid
Away from the normal, because the wavelength must remain constant

Explanation: This question tests understanding of refraction. When light travels from air (lower refractive index) to a liquid with higher refractive index, the light speed decreases. The wave fronts entering the liquid first slow down while those still in air maintain their speed, causing the transmitted ray to bend toward the normal. Choice D incorrectly assumes wavelength remains constant—wavelength actually decreases in the denser medium while frequency stays constant, showing the misconception that wavelength is invariant across boundaries. Remember: light bends toward the normal when entering a denser optical medium.

Question 17

A narrow light ray in air strikes a flat boundary with water at an incident angle of $35^\circ$ to the normal. Water has a higher refractive index than air. Ignore reflection and assume the boundary is smooth. Which way does the ray bend as it enters the water?

Away from the normal, because the speed increases in water
Toward the normal, because the speed decreases in water (correct answer)
Toward the normal, because the frequency increases in water
Away from the normal, because the frequency stays the same

Explanation: This question tests understanding of refraction. When light travels from a medium with lower refractive index (air) to one with higher refractive index (water), the light speed decreases. At the boundary, the wave fronts on the water side travel slower than those still in air, causing the ray to bend toward the normal—like a car wheel hitting sand at an angle. The frequency of light never changes when crossing boundaries, making choice C incorrect based on the misconception that frequency determines bending direction. Remember: when light enters a denser medium (higher n), it bends toward the normal.

Question 18

A ray passes from air into a clear plastic at $65^\circ$ to the normal. The plastic has the higher refractive index ( $n_{plastic} > n_{air}$ ). Compared to the incident ray, the refracted ray in plastic has a angle to the normal.

unchanged angle because the frequency is constant
larger angle because the frequency increases
smaller angle because the speed decreases (correct answer)
larger angle because the speed decreases

Explanation: This question tests understanding of refraction. When light passes from air (lower refractive index) into plastic (higher refractive index), the light speed decreases since v = c/n. At the boundary, the parallel velocity component stays constant while the perpendicular component decreases, causing the ray to bend toward the normal. The refracted ray in plastic makes a smaller angle with the normal than the incident 65°. Choice D incorrectly assumes constant frequency prevents angle change, but while frequency is constant, the speed change still causes bending according to Snell's law. When light slows down entering a denser medium, it always bends toward the normal.

Question 19

A light ray travels from glass into water, striking the boundary at $30^\circ$ to the normal. Glass has the higher refractive index ( $n_{glass} > n_{water}$ ), and the ray transmits into the water. Compared to the incident angle, the refracted angle in water is .

smaller because the speed increases
larger because the frequency increases
larger because the speed increases (correct answer)
smaller because the frequency decreases

Explanation: This question tests understanding of refraction. When light travels from glass (higher refractive index) to water (lower refractive index), the light speed increases since v = c/n. At the boundary, the parallel velocity component stays constant while the perpendicular component increases, causing the ray to bend away from the normal. Therefore, the refracted angle in water is larger than the incident angle of 30°. Choice B incorrectly states frequency decreases, but frequency remains constant across boundaries—it's determined by the source and doesn't change with the medium. When light speeds up entering a less dense medium, remember it bends away from the normal.

Question 20

A light ray in acrylic strikes a boundary with air at an incident angle of $15^\circ$ measured from the normal. Acrylic has the higher refractive index ( $n_{acrylic} > n_{air}$ ), and the ray refracts into the air. Which way does the transmitted ray bend at the boundary?

Toward the normal because the speed increases.
Toward the normal because the frequency increases.
Away from the normal because the speed increases. (correct answer)
No bending because the frequency remains constant.

Explanation: This question tests understanding of refraction. When light travels from acrylic (higher refractive index) to air (lower refractive index), the light speed increases because v = c/n. At the boundary, maintaining continuity of the tangential velocity component while the normal component increases causes the ray to bend away from the normal. The transmitted ray makes a larger angle with the normal than the incident 15°. Choice C incorrectly suggests frequency increases, but frequency is invariant across material boundaries—only speed and wavelength change with the medium. Remember: when light enters a less dense medium and speeds up, it bends away from the normal.