Crazy thing happens when I play with my laser

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In summary, the conversation discusses a person's confusion over the pattern created when shining a green laser at a mirror. They believe the pattern is caused by self-interference, and suggest trying the experiment with tin foil instead. Another person suggests it may be an Airy pattern caused by scattering off a small particle. It is concluded that the pattern is likely due to scattering off a point-like source rather than interference.
  • #1
beholderseye
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I have a strong green laser, about 200 mw. I discovered this a long time ago and have wondered why it does this ever since...

I shine my laser at a mirror. It bounces back, with a brighter beam. That's not what confuses me. What confuses me is when I try to aim the bounceback beam to perfectly intersect with my current beam, I get this CRAZY pattern on the wall right behind my hands:

2459801-blue-water-abstract-background-with-circular-wave-ripple-pattern.jpg


Kind of like this, but the waves get closer and closer together the further from the center.

I am so confused and confounded by this. Can someone explain the physics behind this?
 
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  • #2
I can't speak on the specifics of the situation without a picture of the 'ripples', but what is happening is that the light is interfering with itself which causes an interference pattern, I believe the pattern is circular when a beam is interfering with itself, which would explain this.
 
  • #3
Its weird though, because the pattern, while strongest when the laser hits itself, appears even when the beam is not touching itself but still being reflected off of the mirror.
 
  • #4
Very hard to get a picture of it too.
 
  • #5
beholderseye said:
Very hard to get a picture of it too.

do it anyways, but the answer is interference.
 
  • #6
beholderseye said:
Very hard to get a picture of it too.

I don't blame you!


I can imagine why that happens, and to me it definitely sounds like self-interference.
 
  • #7
Managed to get a video of it.

https://www.youtube.com/watch?v=http://youtu.be/38U2Evzb8jw

 
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  • #8
I would suspect that an interference pattern is being generated from the two interfaces of the mirror.

Try doing the same experiment with the shiny side of tin foil instead of a mirror. I would expect the pattern to be not present if the above hypothesis is true.
 
  • #9
It looks like an Airy pattern, which is what you would get when scattering off a small particle.

If the laser is powerful enough, it can form a defect which it then scatters off in the manner that you recorded in your youtube video.

In short, it is likely scattering off a point-like source rather than interference per se.

Claude.
 

What is causing the unexpected results when I play with my laser?

The unexpected results when playing with a laser could be caused by a variety of factors such as the type and power of the laser, the material or surface it is being pointed at, and environmental factors like air currents or humidity.

Is it safe to play with a laser?

It is generally not safe to play with a laser, especially high-powered lasers. Lasers can cause eye damage and fire hazards if not used properly and with caution. It is important to follow safety guidelines and use protective equipment when handling lasers.

Why do different lasers produce different effects?

Different types and powers of lasers produce different effects because they emit different wavelengths of light. This can affect how the light interacts with different materials and surfaces, resulting in unique visual effects.

Can playing with a laser cause any long-term damage?

Yes, playing with a laser can cause long-term damage to both your eyes and skin. Exposure to high-powered lasers can lead to permanent eye damage and even blindness. The heat and intensity of the laser can also cause burns on the skin.

How can I safely experiment with lasers?

To safely experiment with lasers, it is important to always wear protective eyewear and gloves. Only use lasers that are labeled as safe for personal use and follow instructions carefully. Avoid pointing lasers at people, animals, or reflective surfaces, and always handle with caution.

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