Wave Optics · Question 7

The 8th bright fringe above the point O oscillates with time between two extreme positions. The separation between these two extreme positions, in micrometer ( m), is .

Answer

600.00 to 602.00

Solution

Position of the 8th bright fringe: y8 = 8 Dd = 8 6 10-7 1d = 4.8 10-6d

d varies between 0.76 mm and 0.84 mm.

y = 4.8 10-6 ( 10.76 10-3 - 10.84 10-3 ) = 4.8 10-3 0.1253 m = 6.015 10-4 m

y 601.5 m (the small-change approximation 8 Dd2 2(0.04 mm) gives 600 m)

Answer: 601.50