Visibility of laser light in mist of water particles

[stevenbarea]

Hello, I'm quite intrigued as to why when a mist of water particles (clouds etc) is being shined by laser light, the laser beam is seen clearly, all throughout the mist, but if you take the mist off, the laser beam is no longer seen. What's the theory behind this?


Thanks a lot
From Steven

 

[Doc Al]

You can only see light when it hits your eyes, so unless there's something--like mist or dust--to reflect the light to your eyes, you won't see the beam.