A Wedge of Air

• Parallel fringes appear when glass plates form an air wedge and are viewed in monochromatic light.

• Destructive interference: D = 2 t = m l

• Constructive interference: D = 2 t = (m + 1/2) l.

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This is essentially the same phenomenon as Newton’s rings. Only the geometry of the air layer between the two surfaces is different.