Good surmise.
Shine that into the cockpit of an airliner on approach and someone is going to have a very bad day.
That’s an interesting question, which I’ve checked out the last few times I’ve been to concerts. What happens is that the lasers are carefully positioned so that they don’t aim directly at any of the audience. Instead, they are either aimed above the audience, or at the front of a balcony.
Ah, I was thinking of the handheld lasers that concertgoers might bring to a show and wave about randomly. The ones that are used as part of the performance are indeed very powerful, and yes, they make it a point of not aiming them anywhere that an eyeball might be.
Handheld lasers are absolutely prohibited in any concert I’ve been to.
Lasers used for entertainment are fairly tightly regulated, for obvious reasons. According to the International Laser Display Association:
When used properly , a laser projector is safe. In 40 years of laser light shows, there have been only a handful of reported eye injuries from laser projectors using “continuous wave” lasers. This document goes into great detail about the few injuries, and about the injury potential of laser light shows.
Note the key phrase “when used properly. ” What this means is that light from any Class 3B or Class 4 laser (e.g., over 5 milliwatts) must not be aimed into an audience where it can go into people’s eyes, or where it can be intercepted such as putting a shiny object in the beam path.
The only exception is when the laser show producer has an “audience scanning” variance which specifically allows audience exposure in return for advanced safety procedures and equipment. Such a variance is usually only obtained by professional laser show producers. (If you are interested in this topic, see the pages How to do safe audience scanning and Audience scanning tips.)
Assuming you do not have an audience scanning variance, U.S. federal law requires laser show beams to be at least 3 meters (~10 feet) above where an audience would be reasonably expected to stand, and at least 2.5 meters (8.2 feet) to the side of the audience area. If you follow this guideline, and monitor the audience to ensure they don’t misbehave in an unsafe manner, your shows will be safe.