In Young's double-slit experiment, the light emitted from the source has l = 6.5 x 10^-7 m and the distance between the two slits is 1 mm. The distance between the screen and the slit is 1 meter. Distance between the third dark and fifth bright fringe will be:
Correct answer: B. 1.63 mm
- A. 3.2 mm
- B. 1.63 mm
- C. 0.585 mm
- D. 2.31 mm
Explanation
Fringe position y = m λ D / d (bright) and dark at (m+½)λD/d. Compute positions for third dark (m=2 dark → y = (2.5)λD/d) and fifth bright (m=5 → y = 5λD/d); difference = (5 − 2.5)λD/d = 2.5λD/d ≈ 1.63 mm.
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