# NCERT Class 11 Physics Solutions: Chapter 15 – Waves-Part 7

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Question 15.12:

For the wave on a string described in Exercise , do all the points on the string oscillate with the same,

Frequency,

Phase,

Amplitude?

Explain your answers. What is the amplitude of a point away from one end?

For ;

Frequency,:

Yes, except at the nodes

Explanation:

All the points on the string oscillate with the same frequency, except at the nodes which have zero frequency

Phase:

Yes, except at the nodes

Explanation:

All the points in any vibrating loop have the same phase, except at the nodes.

Amplitude:

No

Explanation:

All the points in any vibrating loop have different amplitudes of vibration.

For;

The given equation is:

For

AmplitudeDisplacement

Question 15.13:

Given below are some functions of to represent the displacement (transverse or longitudinal) of an elastic wave. State which of these represent

A traveling wave,

A stationary wave or

none at all:

Explanation:

The given equation represents a stationary wave because the harmonic terms appear separately in the equation.

Explanation:

The given equation does not contain any harmonic term. Therefore, it does not represent travelling wave or a stationary wave.

Explanation:

The given equation represents a travelling wave as the harmonic terms the combination of

Explanation:

The given equation represents a stationary wave because the harmonic terms appear separately in the equation. This equation actually represents the superposition of two stationary waves.