Why the Newton’s rings are circular and fringes in wedge shaped film are straight?
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1 Answer
The Newton’s rings are circular and the fringes in wedge shaped film are straight because :
The shape of the fringe depends on how the thickness of the air film enclosed varies.
In wedge shaped film the thickness of the air is constant over a straight line along the width of the wedge.
Hence the fringes are straight.
In a newtons ring set up the air film is enclosed below the convex lens. The thickness of the film is constant over a circle (or concentric circles) having center at the center of the lens.
Hence the fringes are circular.
The shape of the fringe depends on how the thickness of the air film enclosed varies.
In wedge shaped film the thickness of the air is constant over a straight line along the width of the wedge.
Hence the fringes are straight.
In a newtons ring set up the air film is enclosed below the convex lens. The thickness of the film is constant over a circle (or concentric circles) having center at the center of the lens.
Hence the fringes are circular.