Figure shows a standard two slit arrangement with slits `S_(1), S_(2). P_(1), P_(2)` are the two minima points on either side of P (Figure). At `P_(2)` on the screen, there is a hole and behind `P_(2)` is a second 2-slit arrangement with slits `S_(3), S_(4)` and a second screen behind them.

Options

A. There would be no interference pattern on the second screen but it would be lighted .
B. The second screen would be totally dark.
C. There would be a single bright point on second screen.
D. There would be a regular two slit pattern on the second screen.

Answer

D

Explanation

At `P_2` minima due to two wave fronts in opposite phase coming from two slits `S_1 and S_2` but thre is wave fronts from `S_1 , S_2 ` . So `P_2` will act as a source of secondary wavelets . Wave front starting from `P_2` reaches mochromatic or coherent sources and will from pattern on second screen.