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I directed a green laser beam on metal sphere and I got this pattern reflected on the wall.

How can we explain the formation of this pattern? Is this interference pattern?

I got this Web pattern when I changed the angle of the Laser beam.

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It is an interference pattern. The surface of the ball is irregular, so it sends light into a range of different directions. On the wall, light from different parts of the spot you've illuminated on the ball interfere with each other to form the pattern you see. The pattern can also be described as a "caustic" pattern [https://en.m.wikipedia.org/wiki/Caustic_(optics)], though there are some differences between coherent and incoherent csustics.

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There is no way to tell without good close up pictures of the ball. More than likely it is the surface pattern of the ball. If it is a brushed metal what you are seeing is the 'grain' look from the sanding. Even if it is polished the magnification from the reflected light off the curved surface will show imperfections from machining it.

Unless there is another source of light to provide alternating wavelengths it cannot be interference.

Drew K

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  • $\begingroup$ My main concern is whether it is an interference pattern or not. $\endgroup$ – Mohammad Al-Turkistany May 17 '17 at 19:24
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    $\begingroup$ The last sentence by @Guydionforge is incorrect. "Alternating wavelengths" are certainly not required for interference. Most examples of interference involve light from a single source; and single wavelength light is ideal for demonstrating interference $\endgroup$ – S. McGrew Dec 25 '18 at 23:36

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