In a Young's double-slit experiment, the fringe width is 1.2 mm. What is the distance between the third bright fringe on one side of the central maximum and the second dark fringe on the opposite side?
Options

Question

In a Young's double-slit experiment, the fringe width is 1.2 mm. What is the distance between the third bright fringe on one side of the central maximum and the second dark fringe on the opposite side?

Options

G1 Physics · Accepted Answer

The third bright fringe is at 3β. The second dark fringe is at 3β ÷ 2. Because they lie on opposite sides, the separation is 3β+3β ÷ 2 = 9β ÷ 2. With β = 1.2 mm, separation = 4.5×1.2 = 5.4 mm. Correct option: C.