Sound — Class 11 MCQs with Answers
Class 11 CBSE Physics · Chapter 302
40 practice questions · 20 Easy · 20 Medium · Updated
Practise the most important Class 11 CBSE Physics questions from Chapter 302, "Sound". You get 4 timed quizzes made from 40 NCERT-based MCQs, with answers and explanations. The questions are split into 20 Easy and 20 Medium. Warm up on the basics, then move on to the exam-level questions that set top scorers in CBSE & Maharashtra HSC Board exams, JEE Main, MHT-CET, JEE Advanced and NEET UG apart.
To score well in "Sound", focus on numericals, derivations and applying concepts. Each MCQ here is timed and uses exam-style marking (+4 correct, −1 wrong, 0 skipped). This trains you to stay accurate under time pressure, as real papers need. Every question has a short explanation, so a wrong answer becomes a quick lesson. It is the fastest way to fix gaps before a test.
Use this chapter for focused revision. Start with the Easy set to check your basics on Sound, then move to Medium to practise applying them. Your accuracy, streaks and XP save automatically. This chapter also adds to your overall Class 11 Physics mastery score. 6 sample questions are solved in full below, with the answer and a worked explanation. Sign in free to start practising.
Key concepts: Sound (Class 11 Physics)
Sound is a longitudinal wave — a train of compressions and rarefactions that needs a material medium to travel. This chapter studies how fast it moves and why. Newton's formula v = √(P/ρ) treated the process as isothermal and gave too low a value; Laplace corrected it by taking the changes to be adiabatic, giving v = √(γP/ρ), which agrees with experiment. The speed is raised by higher temperature (v ∝ √T) and by humidity, and lowered in a denser gas, while pressure alone has no effect. Reflection of sound gives echoes, reverberation and the sonar method of measuring distance. Using the principle of superposition, two waves of nearly equal frequency produce beats of frequency |f₁ − f₂|. Standing waves fix the notes of a stretched string (the sonometer and its laws) and of air columns in open and closed organ pipes, studied experimentally with the resonance tube. Finally the Doppler effect explains why the pitch of a moving source rises as it approaches and falls as it recedes.
- Sound as a longitudinal wave
- Sound propagates as a mechanical longitudinal wave in which particles of the medium oscillate back and forth along the direction of travel, creating alternate regions of compression (high pressure) and rarefaction (low pressure). It cannot travel through a vacuum.
- Newton's formula and Laplace's correction
- Newton assumed sound travels isothermally, giving v = √(P/ρ) ≈ 280 m/s, about 15% too low. Laplace argued the rapid compressions and rarefactions are adiabatic, so the bulk modulus is γP, giving v = √(γP/ρ) ≈ 332 m/s, which matches measurement.
- Factors affecting the speed of sound
- In a gas the speed rises with absolute temperature as v ∝ √T (about 0.61 m/s per °C in air) and increases with humidity because moist air is less dense. It is smaller in a denser gas (v ∝ 1/√ρ), while a change of pressure at constant temperature has no effect.
- Echo
- An echo is the distinct repetition of a sound heard after it reflects from a distant rigid surface. Because the ear separates two sounds only if they are at least about 0.1 s apart, the reflector must be at least roughly 17 m away (at 340 m/s).
Sound — important questions & MCQs with answers (Class 11 Physics)
6 solved questions from this chapter's difficulty levels, each with its answer and explanation. The other 34 are timed and scored when you sign in.
- Q1Easy
While deriving his formula for the speed of sound in a gas, Newton assumed that the compressions and rarefactions take place
A.so rapidly that no heat is exchanged with the surroundingsB.only at very high pressuresC.so slowly that the temperature of the gas remains constant✓ CorrectD.at constant volumeAnswer: C. so slowly that the temperature of the gas remains constant
Explanation: Newton assumed the process is isothermal (temperature constant), so the bulk modulus equals the pressure P, giving v = √(P/ρ).
- Q2Easy
An echo is
A.a sound heard again after being reflected from a distant obstacle✓ CorrectB.the bending of sound around an obstacleC.the increase in loudness of a soundD.the change in pitch of a moving sourceAnswer: A. a sound heard again after being reflected from a distant obstacle
Explanation: An echo is the distinct repetition of a sound produced by the reflection of sound waves from a distant rigid surface.
- Q3Easy
A sound wave travelling through air is
A.a transverse wave, with the air moving at right angles to the waveB.a longitudinal wave, consisting of compressions and rarefactions✓ CorrectC.an electromagnetic waveD.a stationary wave that carries no energyAnswer: B. a longitudinal wave, consisting of compressions and rarefactions
Explanation: In a sound wave the air particles vibrate to and fro along the direction of travel, producing compressions and rarefactions, so it is longitudinal.
- Q4Medium
The speed of sound in air at 0 °C is 332 m/s and it rises by about 0.61 m/s for every 1 °C rise in temperature. The approximate speed of sound at 25 °C is
A.332 m/sB.347 m/s✓ CorrectC.320 m/sD.357 m/sAnswer: B. 347 m/s
Explanation: v = 332 + 0.61 × 25 = 332 + 15.25 ≈ 347 m/s.
- Q5Medium
Taking the speed of sound as 340 m/s and the minimum time gap for an echo as 0.1 s, the minimum distance of a reflecting wall needed to hear a distinct echo is
A.34 mB.68 mC.3.4 mD.17 m✓ CorrectAnswer: D. 17 m
Explanation: The sound must travel to the wall and back in 0.1 s, so distance = (340 × 0.1)/2 = 17 m.
- Q6Medium
Two tuning forks of frequencies 256 Hz and 260 Hz are sounded together. The number of beats heard per second is
A.4✓ CorrectB.8C.2D.516Answer: A. 4
Explanation: Beat frequency = |f₁ − f₂| = |260 − 256| = 4 beats per second.
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Start this chapter free →Sound — FAQs
What are the key concepts in Class 11 Physics Sound?+
Sound is a longitudinal wave — a train of compressions and rarefactions that needs a material medium to travel. This chapter studies how fast it moves and why. Newton's formula v = √(P/ρ) treated the process as isothermal and gave too low a value; Laplace corrected it by taking the changes to be adiabatic, giving v = √(γP/ρ), which agrees with experiment. The speed is raised by higher temperature (v ∝ √T) and by humidity, and lowered in a denser gas, while pressure alone has no effect. Reflection of sound gives echoes, reverberation and the sonar method of measuring distance. Using the principle of superposition, two waves of nearly equal frequency produce beats of frequency |f₁ − f₂|. Standing waves fix the notes of a stretched string (the sonometer and its laws) and of air columns in open and closed organ pipes, studied experimentally with the resonance tube. Finally the Doppler effect explains why the pitch of a moving source rises as it approaches and falls as it recedes. Key ideas include Sound as a longitudinal wave, Newton's formula and Laplace's correction, Factors affecting the speed of sound, Echo.
What does Class 11 Physics Chapter 302 (Sound) cover on XamBaaz?+
It has 40 NCERT-based MCQs on "Sound": 20 Easy and 20 Medium. Together they make 4 timed quizzes, and you never get the same set twice. Every question has an instant explanation. They help you prepare for CBSE & Maharashtra HSC Board exams, JEE Main, MHT-CET, JEE Advanced and NEET UG.
Are these "Sound" questions free to practise?+
Yes. Sign in with Google to practise "Sound" free. Full unlimited access is ₹999/year on a launch offer until 1 December 2026. No chapter is charged separately.
How should I revise "Sound" for the exam?+
Start with the Easy quiz to check your basics, then try Medium to practise applying them. There are 4 timed quizzes on this chapter, so you can come back for a fresh set instead of one you have seen. Read each explanation, retry the questions you miss, and track your accuracy until it stays high.
Are these "Sound" MCQs available with answers?+
Yes. 6 sample questions are shown here in full, each with the correct option and a step-by-step "Why" explanation. Sign in free with Google to start practising, with instant scoring.
Is there negative marking in the "Sound" quizzes?+
Yes. The timed quizzes use exam-style marking: +4 for a right answer, −1 for a wrong one and 0 for a skip, the same negative marking as JEE Main, JEE Advanced and NEET UG. MHT-CET and CBSE board papers have no negative marking. Our mocks for those are scored their way.
What are the important questions from Sound (Class 11 Physics)?+
The questions that matter most test Sound as a longitudinal wave, Newton's formula and Laplace's correction, Factors affecting the speed of sound, Echo. This page shows 6 solved important MCQs with answers and explanations; all 40 questions on the chapter are available as timed quizzes once you sign in.
Is there an online quiz for Sound?+
Yes — Class 11 Physics Sound has timed online quizzes at Easy and Medium levels, with instant scoring and a worked explanation on every question. The first quiz on the chapter is free.