---
title: "AP Physics 2 Unit 14 Practice Test"
description: "A timed AP Physics 2 Unit 14 (Waves, Sound, and Physical Optics) practice test in the AP format, drawn from 1,377 multiple-choice questions and 45 FRQs written for the unit. The standard version takes about 88 minutes."
canonical: "https://fiveable.me/ap-physics-2-revised/unit-test/14"
type: "unit-test"
subject: "AP Physics 2"
unit: "Unit 14"
---

# AP Physics 2 Unit 14 Practice Test

## Overview

A timed AP Physics 2 Unit 14 (Waves, Sound, and Physical Optics) practice test in the AP format, drawn from 1,377 multiple-choice questions and 45 FRQs written for the unit. The standard version takes about 88 minutes.

## Test Format

- 20 Multiple Choice Questions (40 minutes)
- 1 FRQ – FRQ 1 – Mathematical Routines (24 minutes)
- 1 FRQ – FRQ 2 – Translation Between Representations (24 minutes)

## Unit FRQs by Type

- [FRQ 1 – Mathematical Routines](/ap-physics-2-revised/frqs/mathematical-routines?unit=14): 4 questions
- [FRQ 2 – Translation Between Representations](/ap-physics-2-revised/frqs/translation-between-representations?unit=14): 7 questions
- [FRQ 3 – Experimental Design](/ap-physics-2-revised/frqs/experimental-design?unit=14): 18 questions
- [FRQ 4 – Qualitative/Quantitative Translation](/ap-physics-2-revised/frqs/qualitative-quantitative-translation?unit=14): 16 questions

## Practice Questions

### Question 1

Unpolarized light of intensity I₀ is incident on a polarizing filter with a vertical transmission axis. The light then passes through a second filter with a transmission axis at an angle θ to the vertical. Which expression represents the final intensity I_f of the transmitted light?

- (A) I_f = (1/2)I₀ cos²θ
- (B) I_f = I₀ cos²θ
- (C) I_f = (1/2)I₀ sin²θ
- (D) I_f = (1/2)I₀ cosθ

**Answer: (A)** Deriving the final intensity requires applying the 50% transmission rule for unpolarized light followed by Malus's Law. The first filter reduces the intensity to I₀/2, and the second filter transmits (I₀/2)cos²θ based on the angle relative to the polarization axis.

### Question 2

A wave with frequency f travels on a string of linear mass density μ under tension F_T. The wave crosses a boundary onto a second string with linear mass density 9μ under the same tension. Which expression gives the wavelength λ₂ of the wave on the second string?

- (A) λ₂ = (1/3f)√(F_T/μ)
- (B) λ₂ = (3/f)√(F_T/μ)
- (C) λ₂ = (1/9f)√(F_T/μ)
- (D) λ₂ = (1/f)√(F_T/μ)

**Answer: (A)** Deriving the wavelength requires combining the wave speed equation v = √(F_T/μ) with the wave relationship v = λf. Since the density increases by a factor of 9, the speed decreases by a factor of √9 = 3, resulting in a wavelength that is one-third of the original.

### Question 3

A laser beam is vertically polarized with average power P_avg and cross-sectional area A. It passes through a polarizing sheet with a transmission axis at an angle φ to the vertical. Which expression represents the transmitted intensity I_t?

- (A) I_t = (P_avg/A) cos²φ
- (B) I_t = (P_avg/2A) cos²φ
- (C) I_t = (P_avg/A) sin²φ
- (D) I_t = (P_avg/A) cosφ

**Answer: (A)** Deriving the intensity requires defining initial intensity as Power/Area and then applying Malus's Law. Since the incident light is already polarized, the transmitted intensity is the initial intensity multiplied by the square of the cosine of the angle.

### Question 4

A transverse wave travels at speed $$v$$ on a string with tension $$F_T$$. If the tension is increased to $$9F_T$$ while keeping the linear mass density constant, what is the new speed of the wave?

- (A) $$3v$$
- (B) $$9v$$
- (C) $$v/3$$
- (D) $$81v$$

**Answer: (A)** Applying the functional dependence of wave speed on tension ($$v \propto \sqrt{F_T}$$) shows that multiplying tension by 9 increases speed by a factor of $$\sqrt{9} = 3$$.

### Question 5

A string of linear mass density $$\mu$$ supports a wave speed of $$60$$ m/s. If the string is replaced by one with linear mass density $$4\mu$$ under the same tension, what is the new wave speed?

- (A) 15 m/s
- (B) 30 m/s
- (C) 120 m/s
- (D) 240 m/s

**Answer: (B)** Using the relationship $$v \propto 1/\sqrt{\mu}$$, quadrupling the density results in the speed changing by a factor of $$1/\sqrt{4} = 1/2$$. Half of 60 m/s is 30 m/s.

### Question 6

A mechanical wave has an amplitude $$A$$ and carries energy $$E$$. If the amplitude is adjusted to $$0.5A$$, what is the new energy carried by the wave?

- (A) $$0.25E$$
- (B) $$0.50E$$
- (C) $$1.41E$$
- (D) $$2.00E$$

**Answer: (A)** Applying the functional dependence $$E \propto A^2$$, halving the amplitude ($$0.5$$) changes the energy by a factor of $$(0.5)^2 = 0.25$$.

### Question 7

A radio wave with frequency $$f$$ travels through a vacuum at speed $$c$$. If the frequency of the source is increased to $$4f$$, what is the new speed of the wave in the vacuum?

- (A) $$0.25c$$
- (B) $$c$$
- (C) $$2c$$
- (D) $$4c$$

**Answer: (B)** Recognizing that the speed of all electromagnetic waves in a vacuum is a universal constant ($$c$$), regardless of frequency or wavelength.

### Question 8

A string with mass $$M$$ and length $$L$$ is under tension $$F_T$$. A second string with the same mass $$M$$ but length $$2L$$ is placed under the same tension $$F_T$$. How does the wave speed $$v_2$$ on the second string compare to the speed $$v_1$$ on the first?

- (A) $$v_2 = 0.50 v_1$$
- (B) $$v_2 = 0.71 v_1$$
- (C) $$v_2 = 1.41 v_1$$
- (D) $$v_2 = 2.00 v_1$$

**Answer: (C)** Calculating the new linear density $$\mu_2 = M/(2L) = 0.5\mu_1$$. Since $$v \propto 1/\sqrt{\mu}$$, the speed changes by $$1/\sqrt{0.5} = \sqrt{2} \approx 1.41$$.

### Question 9

A sound wave with constant frequency $$f$$ travels through air. If the air temperature increases, causing the speed of sound to increase by 10%, what is the new wavelength $$\lambda_{new}$$ in terms of the original wavelength $$\lambda_0$$?

- (A) $$0.90 \lambda_0$$
- (B) $$1.00 \lambda_0$$
- (C) $$1.10 \lambda_0$$
- (D) $$1.21 \lambda_0$$

**Answer: (C)** Using the functional dependence $$\lambda = v/f$$, if $$v$$ increases by a factor of 1.1 and $$f$$ is constant, $$\lambda$$ must also increase by a factor of 1.1.

### Question 10

Two strings are made of the same material with density $$\rho$$. String B has twice the diameter of String A. If both are under the same tension, what is the ratio of the wave speed on String B to String A ($$v_B/v_A$$)?

- (A) $$0.25$$
- (B) $$0.50$$
- (C) $$1.00$$
- (D) $$2.00$$

**Answer: (B)** Doubling diameter quadruples the cross-sectional area and thus the linear mass density ($$\mu \propto d^2$$). Since $$v \propto 1/\sqrt{\mu}$$, the speed becomes $$1/\sqrt{4} = 1/2$$.

## Review the Unit

- [14.1 Properties of Wave Pulses and Waves](/ap-physics-2-revised/unit-14/1-properties-of-wave-pulses-and-waves/study-guide/Ql0FLnrI6dIHcNlL)
- [14.2 Periodic Waves](/ap-physics-2-revised/unit-14/2-periodic-waves/study-guide/P6HaooQVoZXrucys)
- [14.3 Boundary Behavior of Waves and Polarization](/ap-physics-2-revised/unit-14/3-boundary-behavior-of-waves-and-polarization/study-guide/KovuXqE175SrnAJs)
- [14.4 Electromagnetic Waves](/ap-physics-2-revised/unit-14/4-electromagnetic-waves/study-guide/hZjkcwjYXeKC1jmo)
- [14.5 The Doppler Effect](/ap-physics-2-revised/unit-14/5-the-doppler-effect/study-guide/Qhw4LQ7MLNCPQArz)
- [14.6 Wave Interference and Standing Waves](/ap-physics-2-revised/unit-14/6-wave-interference-and-standing-waves/study-guide/3twkmfrYKPDOuep9)
- [14.7 Diffraction](/ap-physics-2-revised/unit-14/7-diffraction/study-guide/LXB5ClbU33zPgy5z)
- [14.8 Double-Slit Interference and Diffraction Gratings](/ap-physics-2-revised/unit-14/8-double-slit-interference-and-diffraction-gratings/study-guide/K1umdgpBDu7M2fEs)
- [14.9 Thin Film Interference](/ap-physics-2-revised/unit-14/9-thin-film-interference/study-guide/OyOfqxqTZ5XbL7ze)

## Other Unit Tests

- [Unit 9: Thermodynamics](/ap-physics-2-revised/unit-test/9)
- [Unit 10: Electric Force, Field, and Potential](/ap-physics-2-revised/unit-test/10)
- [Unit 11: Electric Circuits](/ap-physics-2-revised/unit-test/11)
- [Unit 12: Magnetism and Electromagnetism](/ap-physics-2-revised/unit-test/12)
- [Unit 13: Geometric Optics](/ap-physics-2-revised/unit-test/13)
- [Unit 15: Modern Physics](/ap-physics-2-revised/unit-test/15)

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