Light intensity through a slit

1. The problem statement, all variables and given/known data
After a laser beam passes through two thin parallel slits, the first completely dark fringes occur at ±14.0∘ with the original direction of the beam, as viewed on a screen far from the slits.

A)What is the ratio of the distance between the slits to the wavelength of the light illuminating the slits?
d/lambda = 2.07

B)What is the smallest positive angle, relative to the original direction of the laser beam, at which the intensity of the light is 110 the maximum intensity on the screen?

Θ=

2. Relevant equations

I = Iocos2(ø/2)

ø = 2∏dsinθ/λ

3. The attempt at a solution

so for this I solved for phi and then substituted that into the second equation and for this sinθ is ≈θ I just solved for theta in the 2nd equation

for ø= 2cos-1(√(1/10))
ø=2.498

then ø/(2∏(d/λ)) = Θ

for Θ I got .192 but I cant figure out what I did wrong

thank you in advance

http://ift.tt/1irLThg

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