How accurate is the laser tape measure? More accurate than steel belt. When you measure a distance greater than about 3 meters, the tape will inevitably sag, so the measurement is not very accurate. green laser pointer measurement working at the speed of light does not have any sagging. Obviously the cheaper model is not accurate, but I would say that even the cheap basement model is better than a tape measure. If I fire a laser beam in a perfect mirror sphere, will the light bounce indefinitely?
Eventually you will absorb light over time. It will glow very quickly inside, and then die out as quickly as the light absorbed from clothes and the body dissipates. Now, if you can shoot a steady stream of light into a sphere with perfect mirror/circular curvature and perfect integrity and precision, the light will eventually scatter and the interior may be as bright as noon, but you won’t It can be seen because anything you put in the mirrored area will act as an absorbent and will disappear quickly when you put it in.
It is like an old analogy: if a tree falls and there is no one around, will it make a sound? It does exist, but if no one around hears it, it’s as if it doesn’t exist. If you shine a laser in a perfect mirror sphere, will it bounce forever? Yes, but there is no way to prove that it is indeed so in the sense of seeing it, because when you open it or put something inside to see it For a moment, it disappeared as fast as it was there.
Sometimes the laser pointer beams diverge because you deliberately spread them with optics. That is a situation. However, even if you want the beam to remain perfectly parallel, it will diverge due to diffraction anyway. You can only reduce divergence by making the beam larger.
The behavior of laser beams is different from other light sources, partly because the light is coherent, and partly because the intensity distribution on the beam diameter is approximately Gaussian rather than uniform. Look up “Gaussian beam optics” to understand their behavior.