Question

A sound is produced by plucking a string in a musical instrument, then

A. The velocity of the wave in the string is equal to the velocity of sound in the string.
B. The frequency of the wave in the string is equal to the frequency of the sound produced.
C. The wave in the string is progressive.
D. The tension in the string varies from point to point.

Answer 1

Hint:
a. Some of the general properties of sound are different in different mediums while few remain the same.
b. Sound waves are different from EM waves in many aspects.

Complete step by step solution:
In order to solve this type of question, we need to analyse each of the given options. Consider option A, which says that
Speed of the wave in the string depends on tension in the string and mass per unit length while the velocity is dependent on elasticity and density. So, both aren’t same and hence,
Considering option B), which states “The frequency of the wave in the string is equal to the frequency of the sound produced.” Now, we know that the sound is produced by the vibration of the string, and hence each vibration in the string would contribute to production of each frequency in the sound.
Let’s have a look at option (C) and (D) as well. Wave in the string is not progressive but a standing wave. Hence (C) is wrong. Also, the tension in the string remains the same at every point, so option (D) is wrong too.

So, we find that option (B) is the only correct option.

Note:
a. The variation in the speed of sound is dependent on the medium and it’s density, because of its longitudinal wave nature. The denser the medium the greater the speed.
b. The string being a denser medium, would surely mean that the velocity of the sound in it is greater than the speed of sound in the air medium.
c. Light and other Electromagnetic waves are transverse in nature, i.e., the vibration in the elements of it’s propagation are in the perpendicular direction to it’s propagational path.