If I is the intensity of light and A is amplitude of the wave, then which of the following is true?

I ∝ \( {A }^{ 3} \) I ∝ \( {A }^{ 1/2} \) I is independent of A I ∝ \( {A }^{ 2} \)

I ∝ \( {A }^{ 2} \)

Intensity always varies as the square of the amplitude.