7.1.7—Intensity = power/area and intensity ∝ (amplitude)2
- Syllabus
- 9702–2028–2029
- Objective
- 7.1.7
- Level
- AS
Intensity is power per unit area and, for a fixed medium, follows amplitude squared
Intensity I=P/A is power crossing unit area. For a wave in a fixed medium, I is proportional to amplitude squared: I∝A².
Keep the area definition separate from amplitude scaling. Doubling amplitude gives four times intensity, not twice.
If a speaker’s amplitude is reduced to one half under comparable conditions, the intensity becomes one quarter.
Intensity is not simply amplitude, and the inverse-square fall with distance is a separate geometric effect.
ConceptA-Level CAIE Physics AS