Intensity

Applied Science: BTEC Level 3 National Extended Diploma, topic 1.7.8

Intensity of Progressive Waves

The intensity of any wave follows the inverse square law.

Inverse square law

Inverse square law

A physical quantity follows an inverse square law if it is proportional to the reciprocal of the distance squared.
The intensity of a wave $I$ is one such quantity, which can be written as:
$I = \frac{k}{d^2}$
Where $d$ is the distance from the wave source and $k$ is the constant of proportionality.

Intensity and power

Intensity and power

By definition, the intensity (I) of any wave is the time-averaged power (P) it transfers per area (A) through some region of space.
The units of intensity are therefore Watts per square metre (Wm^-2).

Test yourself on Intensity

$I = \frac{P}{A}$ only applies to progressive waves. True or false?

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