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Find the angular width of the central maximum.

  • Thread starter bsmm11
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  • #1
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Homework Statement


A single slit of width 1.50 * 10-6m is illuminated with light of wavelength 500.0 nm. Find the angular width of the central maximum.


Homework Equations


θ = λ / b


The Attempt at a Solution


b = 1.50 * 10-6m
λ = 5.000 * 10-7
θ = λ / b = 0.333 = 19.1°

But the answer is 38.9°.

All my calculation of diffraction on single slit is off-target. It seems there is a fundamental point that I am missing. Please help. :frown:
 

Answers and Replies

  • #2
2,449
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You have found the angular position,measured from the centre,of the pattern.There are two such minima,one on each side of the central maxima.
 
Last edited:
  • #3
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OK.. so what I need is 2Θ, right? Then I got 38.2, and this is a bit off from 38.9. Where did this difference come from?
 
  • #4
2,449
87
I calculated it to be 38.9.The equation is:
sin theta=lambda/d.
Did you take theta to be in radians?If so that is a good approximation but only for very small angles.
 
  • #5
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  • #6
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Now I can solve the problems. Thanks everyone!! :D

p.s. Emily, the link is not valid. Could you give me a right one? I can solve the problems, but still I want to check it out.
 

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