Question

Using a 687 nm wavelength laser, you form the diffraction pattern of a 1.1 mm wide slit on a screen. You measure on the screen that the 14th dark fringe is 9.11 cm away from the center of the central maximum. How far is the screen located from the slit? The answer is not 10.419 m

Answer 1

Using the diffraction pattern,

For a dark fringe

dsin = m

Using small angle approximation,

sintany/D

So, the formula,

dy/D = m

Where, d = 1.1*10^-3 m, y = 0.0911 m, m = 14 , = 687*10^-9 m Calculate D

D = 1.1*10^-3 0.0911/14*687*10^-9

= 10.0 m

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