ACOUSTICS · Part 2

kHz, Human ear cannot detect these waves, but certain creatures like mosquito, dogs, bats, dolphins can detect these waves. e.g., waves produced by bats. . . Difference between the sound and light waves S.No. SOUND LIGHT Medium is required for the propagation. Medium is not required for the propagation. Sound waves are longitudinal. Light waves are transverse. Wavelength ranges from . cm to . m. Wavelength ranges from × – m to × – m. Sound waves travel in air with a speed of about ms – at NTP. Light waves travel in air with a speed of × ms – . . . Velocity of sound waves When you talk about the velocity associated with any wave, there are two velocities, namely particle velocity and wave velocity. SI unit of velocity is ms - Acoustics Particle velocity: The velocity with which the particles of the medium vibrate in order to transfer the energy in the form of a wave is called particle velocity. Wave velocity: The velocity with which the wave travels through the medium is called wave velocity. In other words, the distance travelled by a sound wave in unit time is called the velocity of a sound wave. ∴ Velocity = Distance Time taken If the distance travelled by one wave is taken as one wavelength (λ) and, the time taken for this propagation is one time period (T), then, the expression for velocity can be written as ∴ V = λ T ( . ) Therefore, velocity can be defined as the distance travelled per second by a sound wave. Since, Frequency (n) = /T, equation ( . ) can be written as V = nλ ( . ) Velocity of a sound wave is maximum in solids because they are more elastic in nature than liquids and gases. Since, gases are least elastic in nature, the velocity of sound is the least in a gaseous medium. So, v S > v L > v G . . Factors affecting velocity of sound In the case of