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In a cloudy chamber (filled with water vapour for arguments sake), it is possible to see a laser beam and if two beams intersect, the point of intersection will be presumably brighter. enter image description here

Is it possible to stop the point of intersection being brighter by flashing the beams at a high frequency in a way that both beams will not be on at the same time?

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Assuming that the distance to the intersection point of the beams is equal, you would have to toggle each laser on and off at the frequency of the time for light to travel twice the distance to the intersection. Secondly you would have to put the lasers out of phase. What happens is that for half a phase, laser one will be beaming, and for the second half of the phase, laser two will be beaming. A bit like traffic and stop signs.

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  • $\begingroup$ What is the reason for the lights having to toggle twice the distance of the point of intersection? Also, how precise does the toggle speed have to be? $\endgroup$ – zaka100 Jan 7 '17 at 20:18
  • $\begingroup$ It is twice because a phase consists of one active part and one inactive part. So during one phase, first laser one is on and laser two is off, and vice versa for the second half of the fase. As each half lasts a the time for light to the intersect, a complete fase lasts twice that time. The toggle speed would have to be spot on for perfect results. Any deviation from that speed would be visible as a brighter point of intersection. The impact of this would depend on the actual distance, as the frequency would lower when the distance increases. May I ask what you were intending using this for? $\endgroup$ – Sebas Smits Jan 7 '17 at 20:53
  • $\begingroup$ Well, i was just curious about a holography concept i thought of but a flaw in it would be that there would be unwanted intersections and I am thinking of a way to get rid of them. A problem is that the lasers would be at different distances from the point of intersection so that may require extra calculations. $\endgroup$ – zaka100 Jan 7 '17 at 22:04

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