Wave intensity is the rate at which energy transmits per unit area, across a surface perpendicular to the direction of propagation of the wave. In other words, it is power transmitted per unit area. Mathematically,

Intensity (I) = $\frac{\text{Energy (E)}}{\text{Area (A) × Time (t)}}$
Intensity is directly proportional to the square of amplitude and inversely proportional to the area.

The energy in a wave is transmitted in this way: as a particle vibrates, it pushes its neighbour, transferring energy to it. Then, the neighbouring particle repeats the process.

The frequency (f) of a wave is the reciprocal of the time period (T).
Frequency (f) = $\frac{\text{1}}{\text{Time Period (T)}}$
The speed of a wave is defined as the distance travelled by a point on the wave in a given amount of time.

Speed (v) = $\frac{\text{Distance (d)}}{\text{Time (T)}}$

Wave speed can also be calculated using the equation:
Wave speed (v) = frequency (f) wavelength (λ).

From this equation, it can be inferred that the speed of the wave is independent of the amplitude of the wavebut depends upon the wavelength and the frequency.
Time period is the time taken by a wave to complete one cycle, whereas wavelength is the distance covered by the wave in one cycle.
When a wave covers a distance of one wavelength, then each particle undergoes one oscillation.

Theparticles that move in the same direction and have the same displacement are known as inphase particles. In-phase particles are one wavelength apart from each other.

7.02 - Progressive Waves II

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