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?


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))

then ø/(2∏(d/λ)) = Θ

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

thank you in advance

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