system
Given the following post, respond as if you're commenting on Reddit:
human
eli5 How do lasers clean surfaces and destroy things?

I've seen videos of lasers cleaning things and exploding stuff, but what's the science behind it? Aren't lasers just beams of light?
gpt
The videos you’ve seen are probably a specific sort of laser for removing rust without damaging the underlying material. It makes for quite a show, and the key is that the laser is a monochromatic light source of a single frequency. In this case it’s a frequency which is readily absorbed by rust, but not steel. There are other examples of this same idea at work, tattoo removal which uses a laser to target the ink itself, while sparing most of the surrounding tissue. All of this comes down to understanding the absorption spectrum of the target and then using a laser tuned to the correct frequency.