Class 10 > Unit # 10: General Waves Properties > Characteristics of waves

Define the Characteristics of Waves

Video Lecture

i) Time Period

Definition: The time required by one point on a wave to complete one vibration (or one cycle) is called Time Period.

It is denoted by symbol \(T\) and its S.I. unit is second (s).

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ii) Frequency

Definition: The number of waves produced by any source in unit time (1 second) is called frequency.
(OR: The number of waves passing through a point in unit time is called frequency.)

It is denoted by symbol \(f\) and its S.I. unit is Hertz (Hz).

\[ f = \frac{1}{T} \]

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iii) Wavelength

Definition: The linear distance between two consecutive crests or troughs is called wavelength of that wave.
(OR: The linear distance between two consecutive compressions or rarefactions is called wavelength.)

It is denoted by the Greek letter \(\lambda\) (lambda) and its S.I. unit is meter (m).

Figure 1: Diagram showing crests, troughs, and wavelength (\(\lambda\)) of a transverse wave.

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iv) Wave Speed

Definition: The speed by which a wave travels through a medium is called wave speed.

It is denoted by symbol \(v\) and its S.I. unit is meter per second (m/s).

Derivation of Wave Equation (\(v = f\lambda\)):

Let \(\lambda\) be the distance covered by a wave in time period \(T\). According to the standard definition of speed:

\[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} \implies v = \frac{\lambda}{T} \quad \text{--- (i)} \]

As we know, frequency is the reciprocal of the time period:

\[ f = \frac{1}{T} \]

Substituting this relationship into equation (i), we get:

\[ v = f \cdot \lambda \]

Conclusion: Wave speed is equal to the product of the frequency and wavelength of that wave.

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v) Wave Front

Definition: A wavefront is an imaginary line or surface on a wave that joins all adjacent points vibrating in the same phase. Wavefronts are usually drawn by connecting all consecutive crests.

There are two primary types of wavefronts depending on how waves are produced:

• Plane Wavefronts (Parallel Straight Lines): Produced in a ripple tank when a flat or plane horizontal dipper strikes the surface.
• Circular Wavefronts (Concentric Circles): Produced in a ripple tank when a spherical or point-dipper strikes the surface.

Figure 2: Plane wavefronts (straight parallel lines) vs. Circular wavefronts (concentric circles).