Consider the setup shown in the figure. Two slits S₁ and S₂ are placed symmetrically around the central line and are illuminated by a monochromatic light of wavelength . The separation between the slits is d . The light transmitted by the slits falls on a screen ₁ placed at a distance D from the slits. Slit S₃ is on the central line and slit S₄ is at a distance z from S₃ . Another screen ₂ is placed a further distanc

Step-by-step solution

The path difference for light reaching a point at a distance y from the central axis on screen ₁ is given by x = y d D . Since slit S₃ is on the central line ( y = 0 ), the path difference is x₃ = 0 . Thus, the intensity at S₃ is maximum, let it be I₀ . Slit S₄ is at a distance z = D 2d from the central line. The path difference at S₄ is: x₄ = z d D = ( D 2d ) d D = 2 A path difference of 2 corresponds to destructive interference. Therefore, the intensity at S₄ is 0 . Since slit S₄ receives no light, it acts as a s