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Course Contents » » HW #8 (07/26 Th 11:59 PM) » Diameter of a wire TimerNotesEvaluate Feedback Print The diameter of a thin wire is measured in a physics laboratory by a student. The wire is held vertically in a holding frame in front of the laser beam. The laser light diffracts on the wire and produces a diffraction pattern on a white screen. The diffraction pattern is shown in the fiqure. The pattern is centered around the origin gure. -2 -3 x (cm) The wavelength of the laser light is 424 nm, and the screen is 1.91 m away from the wire. What is the diameter of the wire? (Hint: one of the higher order diffraction minima lines up with a well defined x-value. Also, it is perfectly safe to use the small angle approximation : sin(?) = tan(? 6.073 10-5 m Submit Answer Incorrect. Tries 4/12 Previous Tries

Explanation / Answer

Given,

Wavelength lambda = 424 nm

Distance d = 1.91 m

diameter of thin wire is the slit width a

third order minimum is at a distance x=4 cm from central maximum.

For diffraction, a sin(theta) = n * lambda

since angles are small sin(theta) = tan(theta)

a * (0.04 / 1.91) = 3 x 424 x 10^-9

a = 60.74 x 10^-6 m = 60.74 ?m (Ans)

Comment in case any doubt please rate my answer....

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