51 Laser light of wavelength ? passes through a thin slit of width a and produce

Question

51 Laser light of wavelength ? passes through a thin slit of width a and produces its first dark fringes at angles of +20.0o with the original direction of the beam. What is the new distance of the first dark fringe in the screen fringe Yo A. (3)0% ?. ??, if slit width is reduced by 3? Report the results in the unit of the initial distance of the D. 1/3 Yo E. None of above. 52. What is the smallest separation between two pointlike objects that a person could clearly resolve at his near point of 18.0 cm with a pupil diameter of 2.50 cm? Assume that the light has a wavelength of 504 nm. A. 1.96 um B. 12.3 pm C. 59.8 um D. None of above.

Explanation / Answer

51. sin(20) = 1 lambda / a = K  

K = 0.342

and Y0 = D tan20 = 0.364 D  

Now if a = a0/3 then sin(theta) = 3 K = 1.09

so there will be no dark fringe.

Ans(E)

52. Resolution = 1.22 lambda / D

R = (1.22)(504 x 10^-9) / (2.50 x 10^-2)

R = 2.46 x 10^-5 rad

d = (2.46 x 10^-5)(0.18) = 4.43 x 10^-6  

Ans(D)

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