How does a laser attenuate with distance?

Question

Arduino

Approximate data for laser systems of several hundred milliwatts ordered in China.
How to approximately estimate what power (thermal effect) the laser will have N meters after the source?

Answer 1

See the air transmission spectrum in the visible range. For a violet laser (405 nm), the transmittance is approximately 0.7 per 1 km, for green (532 nm) - 0.8, for red (650 nm) - 0.85

Answer 2

It seems that at a distance of about 10-20 meters, losses from absorption and scattering can be neglected. At distances of the order of several kilometers, the attenuation will be significant, especially in the blue region. The thermal effect will rather depend on the size of the spot.