Red light of wavelength 633 nm from a helium-neon laser passes through a slit 0.

Question

Red light of wavelength 633 nm from a helium-neon laser passes through a slit 0.310 mm wide. The diffraction pattern is observed on a screen 3.25 m away. Define the width of a bright fringe as the distance between the minima on either side.

Problem 26.28 Red light of wavelength 633 nm from a helium- neon laser passes through a slit 0.310 mm wide. The diffraction pattern is observed on a screen 3.25 m away. Define the width of a bright fringe as the distance between the minima on either side. Part A What is the width of the central bright fringe? 13.27 Submit My Answers Give Up incorrect; Try Again; 5 attempts remaining Part B What is the width of the first bright fringe on either side of the central one? 19.03 Submit My Answers Give Up incorrect. Try Again. 5 attemnts remaining

Explanation / Answer

condition for diffraction maximum is

d sin theta1 = m lamda

theta1 = ( m lamda/ d)

= ( 1 * ( 633 * 10^-9) /0.310 * 10^-3)

=2.041 * 10 ^-3 rad

y1 = L tan theta = 3.25 tan 2.041* 10^-3 rad = 6.63* 10^-3 m

w = 2 y1 = 13.26 mm

W = y2 - y1

sin thet2 = 2 lamda/d

theta 2 = 2 ( 633* 10^-9/0.310* 10^-3) = 4.083 * 10^-3 rad

y2 = L tan theta = 3.25 tan 4.083 * 10^-3 = 1.327 * 10^-2 m

w = y2 - y1 =1.327 * 10^-2 m-   6.63* 10^-3 m=6.64 mm

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