Newton's rings by reflection

Classical convex/plane glass contact using an opal-glass diffuser illuminated by: left - a 6500K LED lamp (continuum); middle - an energy-saving mercury fluorescent bulb (complex spectrum); and, right - a 532nm laser (monochromatic).

This illustrates the rapid (colour overlap) smearing of the fringes with continuous spectrum illumination. The Hg lamp has several strong emission bands/lines which result in a 'beating' pattern of the fringes at higher orders (larger radius).

The green laser image has a 'speckled' appearance produced by localised interference due to the coherence of the laser light.

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