What is Transverse Wave motion?

 

 

What is Transverse Wave motion?

 

First we discuses about some more points regarding to previous blog

 

(ii) If the free end of the slinky is pushed and pulled at regular intervals, a series of compressions and rarefactions are set up in the slinky which follow each other at regular intervals.

 

(iv) If a dot (D) is marked on the slinky, it is found to move back and forth.

 

Thus, we conclude that the loops of the slinky move back and forth in the same direction in which a wave comprising of compression and rarefaction travels. This type of wave is called a longitudinal wave.

 

Hence, a sound wave which propagates as a series of compressions and rarefactions is a longitudinal wave. In general,

 

A wave motion is said to be longitudinal if the particles of the medium through which the wave propagates vibrate in a direction parallel to the direction of propagation of the wave.

 

TRANSVERSE WAVE MOTION

 

Apart from longitudinal wave motion, there is another type of wave motion, called the transverse wave motion. In a transverse wave motion, the particles oscillate up and down about their mean positions along the direction of propagation of the wave Thus,

 

A wave-motion is said to transverse if the particles of the medium through which the wave propagates vibrate in a direction perpendicular to the direction of propagation of the wave.

 

 

Unlike longitudinal waves, there is no pressure (or density) variation in case of transverse waves. En fact, transverse waves involve changes in the shape of the medium.

 

A transverse wave is propagated in the form of crests (C) and troughs (T).

 

(a) Crest. The hump or elevation in a medium through which a transverse wave is passing is called a crest

(b) Trough. The hollow or depression in a medium through which a transverse wave is passing is called a trough.

 

The distance between the centres of two consecutive crests or troughs is called the wavelength.

 

A few examples of transverse wave motion are:

 

(i) Waves produced when a string stretched between two points is plucked at the centre. The portions of the string where the displacement is positive are called crests and the portions where it is negative are called troughs.

 

(ii) Light waves, heat waves, radio waves. These waves do not need a medium for their propagation as these are not mechanical waves.

 

You will learn in Class XII that these waves, are in fact, electromagnetic waves. 1. Sound is mechanical energy which produces sensation of hearing.

 

On Your Tips

 

2. Sound is produced due to vibration of different objects.

 

 

3. A material medium is essential for the propagation of sound as it cannot travel in vacuum.

 

4. A region of compressed air (increased density or pressure) is called a compression and that of rarefied air (decreased density or pressure) is called a rarefaction.

 

5. A wave motion is a form of disturbance (a mode of momentum and energy transfer) which is due to repeated vibrations of the particles about their mean positions and the motion is transferred from ove particle to the other without any net movement of the medium. A wave motion is of two types : (i) Longitudinal (ii) Transverse.

 

6. Sound wave propagates as compressions and rarefections (i.e., as variations in density or pressure) in the medium.

 

7. As sound propagates, it is the sound energy that travels in the medium and not the medium itself.

 

8. Sound waves are longitudinal waves. Light waves, on the other hand, are transverse waves.

 

VARIATION IN PRESSURE AND DENSITY OF MEDIUM DUE TO SOUND WAVE

 

As said earlier, a sound wave is a longitudinal wave which travels in the form of compressions and rarefactions which are defined as follows.

 

Compression. A portion of the medium where a temporary reduction in volume and consequently an increase in density (and pressure) takes place when a sound wave passes through the medium is called a compression or condensation,

 

In a compression, the particles of the medium lie closer to each Rarefaction. A portion of the medium where a temporary increase in volume and consequently a decrease in density takes place when a sound wave passes through the medium is called a rarefaction. In a rarefaction, the particles of the medium lie farther apart than the normal distance between them other than they normally are.

 

The variation in pressure and density when a sound wave travels in a medium is shown in the graph of a few important terms connected with a sound wave follow from this graph.

 

(2) A compression is represented by a peak and a rarefaction by a valley (i.e., the lower portion of the

 

curve). A peak is called the crest and a valley is called the trough of the wave. (b) The points of maximum density (or pressure) and minimum density (or pressure) are also called crests and troughs respectively.

 

(C) Amplitude (A). The magnitude of the maximum disturbance in the medium on either side of the mean position is called the amplitude of the wave. It is usually represented by the letter A. In case of sound, the unit of A is the same as that of density or pressure.

 

(d) Oscillation. As is clear from the graph, the density (or pressure) of the medium oscillates between a maximum value and a minimum value. The change in density (or pressure) from marimum value to the minimum value and again to the maximum value is called an oscillation.

 

(e) Frequency (v). Frequency enables us to know as to how many times does a particular event occur in a given time. If you count your pulse, you may find that it throbs around 72 times per minute. This is expressed by saying that the frequency of the pulse is 72 time per minute. Similarly, the frequency of a sound wave is defined as the number of complete oscillations in density (or pressure of the medium) per second. It is denoted by the symbol v (Greek letter, nu).

Thank You!