Intensity of Waves
Physics: Cambridge International A Level, topic 7.2.2
Intensity of Progressive Waves
The intensity of any wave is defined as the time-averaged power transferred per area of space. The intensity is proportional to the square of the amplitude of the wave.
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).
Intensity and amplitude
- The energy of a wave is proportional to the square of its amplitude. Therefore the intensity of a wave is also proportional to the square of its amplitude.
Implication
- We often deal with waves propagating through space, where the intensity varies as an inverse square law with distance from the source of the waves.
- Therefore, the amplitude of the wave must fall as a simple inverse proportion to distance.
Test yourself on Intensity of Waves
only applies to progressive waves. True or false?