JEE Main 2011 Physics question
Direction: The question has a paragraph followed by two statements, Statement −1 and statement −2. Of the given four alternatives after the statements, choose the one that describes the statements. A thin air film is formed by putting the convex surface of a plane - convex lens over a plane glass plate. With monochromatic light, this film gives an interference pattern due to light reflected from the top (convex) surface and the bottom (glass plate) surface of the film. Statement-1 : When light reflects from the air-glass plate interface, the reflected wave suffers a phase change of π. Statement-2 : The centre of the interference pattern is dark.
Solution
Reflection at the air–glass plate interface (from a rarer to a denser medium) introduces a phase change of π — Statement 1 is true. At the centre the air film has zero thickness, so the only phase difference between
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