# How can I measure the amplitude of a light wave?

Suppose I have a light wave and I want to measure its amplitude, or check to see if it has an amplitude of a certain value: how would one go about doing this?

• Use a photodiode: en.wikipedia.org/wiki/Photodiode. There are very expensive calibrated ones, but even the uncalibrated ones are useful for most purposes and they are reasonably priced (in the $1-10 range) e.g. mouser.com/ProductDetail/Vishay-Semiconductors/BPW20RF/…. Be aware that you are really measuring intensity ($W/m^2\$) by measuring the photocurrent. If you want to measure really large areas, use a solar cell. They are basically very large photodiodes, just not as precise. – CuriousOne Jun 2 '16 at 21:22