(chatquestion)...Figure shows sound waves of wavelength are emitted by a point source S and travel to a detector D directly along path 1 and via reflection from a panel along path 2. Initially, the panel is almost along path 1 and the waves arriving at D along the two paths are almost exactly in phase. Then the panel moved away from path 1 as shown until the waves arriving at D are exactly out of phase, the path difference Ax of the waves along the two paths Panel S O D λ (а) 0 (b) 4 32 (c) (d)...(Photo from Aayush)

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