Name: Musical Instruments
Uploaded: 2019-07-19
Duration: 10 min
Description: There is science in music and music in science. All musical instrument create pleasant sounds, but the science behind one is different from the other. Learn...

Question

Describe the process of propagation of sound in air with the help of suitable diagram. Draw the graph of density versus position for a sound wave.

Accepted Answer

a. When the prongs of a tuning fork are not vibrating, the vertical lines representing the air particles or layers are equidistant (Fig.a).

b. When the prongs of the tuning fork are struck against a hard rubber pad, the prongs begin to vibrate. When the prongs move to the right, i.e. towards n from the mean position m, they compress the layer of air in contact with it. The volume of these layers at C decreases and pressure increases (as compared to the adjacent layers). This pressure difference causes the compressed layer to move forward, without the air layer moving forward. It compresses the next layer and so on. Thus, a wave of compression travels onwards to the right. The disturbance thus passes on from one layer to the next, but the layers themselves do not move with the disturbance (Fig.b).

c. When the prong returns from n to the mean position m, the compression travels onwards from C to C₁ (Fig.c).

d. When the prong from the mean position m reaches the other extreme position I, the pressure of the air layers adjoining the prong decreases and volume increases. The particles of air which had moved to the right, now move to the left. While returning, the particles overshoot their mean position due to inertia of motion leading to the expansion of air layers near the prong, thus producing rarefaction R. The compression shifts from C₁to C₂, (Fig.d).

e. When the prong returns from the extreme position I to the mean position m, (thus completing one vibration), the rarefaction R shifts to R₁, the compression shifts from C₂ to C₃ (Fig.e). Thus, the vibrating prong of a tuning fork produces a source of alternating compression and rarefaction in air that travel forward with the speed of the wave.

When the sound waves propagates in a medium, the variation in density and pressure forming compression and rarefaction can be represented as shown below.

Compressions are the regions where particles are crowded together and are represented by upper portion of the curve. The peak represented the maximum compression. Here, the density and pressure are highest. Rarefactions are the regions where particles are far away from each other. Here, density and pressure are low and are represented by the lower portion of the curve.

Describe the process of propagation of sound in air with the help of suitable diagram. Draw the graph of density versus position for a sound wave.

Important Questions on Sound

Learn and Prepare for any exam you want !