# NCERT Class 11 Physics Solutions: Chapter 15 – Waves-Part 8

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**Question 15.14:**

A wire stretched between two rigid supports vibrates in its fundamental mode with a frequency of 45 Hz. The mass of the wire is and its linear mass density is what is

The speed of a transverse wave on the string, and the tension in the string?

**Answer:**

Mass of the wire,

Linear mass density,

Frequency of vibration,

∴Length of the wire,

The wavelength of the stationary wave is related to the length of the wire by the relation:

Where, Number of nodes in the wire.

For fundamental node,

The speed of the transverse wave in the string is given as:

The tension produced in the string is given by the relation:

**Question 15.15:**

A meter-long tube open at one end, with a movable piston at the other end, shows resonance with a fixed frequency source (a tuning fork of frequency ) when the tube length is. Estimate the speed of sound in air at the temperature of the experiment. The edge effects may be neglected.

**Answer:**

Frequency of the turning for

Since the given pipe is attached with a piston at one end, it will behave as a pipe with one end closed and the other end open, as shown in the given figure:

Such a system produces odd harmonics. The fundamental note in a closed pipe is g by the relation:

Where,

Length of the pipe,

The speed of sound is given by the relation: