28. Wave Optics question bank (Physics)

In a Young’s double slit experiment a point source emits monochromatic light. Two closely spaced slits 1 and 2 are made in an opaque board and the source is placed symmetrically as shown in the figure. The opaque board can be shifted vertically as well as horizontally. Fringes are observed on the screen placed at a distance \(D\) from the opaque board. As the source and the opaque board are shifted, the observation of fringes on the screen changes. These are listed in the following columns. Match the columns.

Column I shows four situations of standard Young’s double slit arrangement with the screen placed far away from the slits \(S_1\) and \(S_2\). In each case, \(S_1P_0=S_2P_0\), \(S_1P_1-S_2P_1=\lambda/4\) and \(S_1P_2-S_2P_2=\lambda/3\), where \(\lambda\) is the wavelength of the light used. In cases (B), (C) and (D), a transparent sheet of refractive index \(\mu\) and thickness \(t\) is pasted on slit \(S_2\). The thickness of the sheets are different in different cases. The phase difference between the light waves reaching a point \(P\) on the screen from the two slits is denoted by \(\delta(P)\) and the intensity by \(I(P)\). Match each situation in column I with the statement(s) in column II valid for that situation.