# Relationship between intensity and amplitude of light wave

I am confused with the realtionship between intensity and amplitude of wave. My understanding is that energy in a wave is proportional to its intensity; which is proportional to the square of the maximum height of the wave. is that a correct understanding.? If that understanding is correct I have a red right and I increase the brightness what happens.? Do I increase the amplitude of the wave.?

The maximum height of a wave is also referred to as it's amplitude, and yes, you are correct. The energy of a wave is proportional to the square of it's amplitude, and by consequence, it's intensity depends on the square of $$A$$ as well. If the intensity were to decay as $$1/r^2$$ then it's amplitude would decay as $$1/r$$ as well. Increasing the brightness of your light would give it a larger amplitude and thus a larger intensity as well.