DC Pandey Sound Waves Solutions

DC Pandey Waves and Thermodynamics Solutions for Chapter 16 ‘Sound Waves’ will assist you to solve the exercise questions of the chapter easily. Displacement Wave, Density Wave, and Pressure Wave are some of the main concepts that are covered in this chapter of DC Pandey Physics Book Solutions. You will also learn the formula to find the speed of the longitudinal waves and the intensity of the sound waves in gases. Other topics related to sound waves included in this chapter are interference of sound waves, standing longitudinal waves in organ pipes, beats and the Doppler Effect. 

In DC Pandey Sound Waves Solutions, the set of 155 questions in 3 exercises will help you in preparing all the topics thoroughly. You will able to find the amplitude, frequency, and speed of the longitudinal sound waves after practising the exercise questions extensively. The paper pattern of important exams like JEE Mains and JEE advanced is covered comprehensively by including questions based on assertion-reasoning, multiple-choice questions, match the columns, fill in the blanks, and long-answer type numerical questions in the exercises. 

Solutions of exercise questions in DC Pandey Chapter Sound Waves will help you to develop an aptitude for approaching the questions using the right formula at the Instasolv platform. The answers are written in a language that is easy to understand. Our experts use the simplest possible methods to solve all the exercise questions. If you employ discipline in your daily routine with reliance on Instasolv for assistance, you will definitely get through your desired entrance exams.

Important Topics for DC Pandey Waves and Thermodynamics Solutions Chapter 16: Sound Waves


The audible range of the human ear in the sound waves is from a frequency of 20 Hz to 20000 Hz. In this chapter sound waves in air is discussed with utmost importance while we know that sound waves can traverse through any mediums.

Displacement Wave, Density Wave, and Pressure Wave

A sound wave can be expressed as a function of the displacement or the oscillation of particles of air about their equilibrium position y(x,t) as a function of change in pressure of the medium ΔP(x,t), or the density fluctuations Δρ(x,t).

The displacement in longitudinal waves is along the direction of propagation of the wave and cause the density and pressure fluctuations.

Relationship between displacement wave and pressure wave: Pressure variation and displacement of the particle remain 90 degree out of phase.

Relationship between pressure wave and density wave: The density equation of wave remains in phase with the pressure equation. Both these equations are out of phase with respect to the displacement equation with 90 degree.

Speed of Longitudinal Wave

The speed of a longitudinal wave is calculated by assuming an elemental mass of density ρ and surface area S and applying newton’s second law of motion using the changes in its position and pressure variations around it. 

Thus, the speed, v of the longitudinal wave in a fluid is given as,

Speed of a longitudinal wave in a solid medium is given as,

Sound Waves in Gases

For frequencies ranging from 20 Hz to 20000 Hz, the process of propagation of a sound wave remains nearly adiabatic. Thus for speed, we use the Adiabatic Bulk Modulus given as BsP such that λ=Cp/Cv and ρ=PM/RT. Now speed, 

Effect of Temperature on Sound Wave in Air:

The speed of sound increases by approximately 0.61 m/s per degree Celsius rise in temperature.

Effect of Pressure on Sound Wave in Air:

There is no impact of pressure variation on the speed of the sound wave in the air.

Effect of Humidity on Sound Wave in Air:

In moist air, the speed of sound was found to be greater than the speed of sound in dry air.

Sound Intensity

Sound Intensity is given by the formula,

Interference of Sound Waves

The phase difference can be denoted with respect to position and time as,

The sources that have constant phase difference or are in phase are called coherent sources.

Therefore, for constructive interference and destructive interference φ=2nπ and φ=(2n+1)π, respectively, hold true.

Hence,  for constructive interference,

For destructive interference,

Standing Longitudinal Waves in Organ Pipes and Beats

Pressure Equation is given as,

In a closed organ pipe, frequencies oscillate in harmonic series that include only odd integer multiples of the fundamental frequency. In an open pipe, frequencies oscillate in harmonic series that include all the integral multiples of the fundamental frequency.

Beat frequency, f is given as, f=f1f2

Doppler Effect

This concept defines the frequency experienced by the observer and the original frequency when the source and receiver are in motion.

Exercise Discussion for DC Pandey Waves and Thermodynamics Solutions Chapter 16: Sound Waves

Introductory Exercises:

  • Exercise 16.1 and 16.2 will require you to calculate bulk modulus, displacement and pressure amplitudes and the speed of the wave.
  • Exercise 16.3 covers the questions based on the intensity of sound waves.
  • In exercise 16.4, you will learn to find the phase difference and amplitudes of sound waves based on constructive and destructive interference.
  • You will learn to calculate displacement and pressure amplitudes of antinodes in the organ pipes and other concepts related to the organ pipe.
  • Exercise 16.6 is based on tuning forks that employ the concepts of beats.
  • In 16.7, you will get to solve complex problems of the Doppler Effect.

Exercise for JEE Main:

There are 37 subjective questions in which you will be required to find the amplitude, velocity, wavelengths, frequency of the longitudinal sound waves and 34 multiple-choice questions.

Exercise for JEE Advance:

This exercise consists of high-level numerical questions based on Doppler Effect, longitudinal standing waves, beats and other concepts of longitudinal sound waves. 

Why Use DC Pandey Waves and Thermodynamics Solutions Chapter 16: Sound Waves by Instasolv?

DC Pandey Waves and Thermodynamics Solutions for Sound Waves provided by the expert faculties at the Instasolv platform consist of highly accurate and precise answers. You can rely on us to get step by step help with adequate reasoning in every question of the DC Pandey Exercise Solutions book.