I do have the right calculations but for some reason I am not getting the right

Question

I do have the right calculations but for some reason I am not getting the right answers for these two questions. Please help me thanks.

(1) A beam of monochromatic green light is diffracted by a slit of width 0.450 mm. The diffraction pattern forms on a wall 2.06 m beyond the slit. The distance between the positions of zero intensity on both sides of the central bright fringe is 4.10 mm. Calculate the wavelength of the light.

2. A possible means for making an airplane invisible to radar is to coat the plane with an antireflective polymer. If radar waves have a wavelength of 3.00 cm and the index of refraction of the polymer is n = 1.40, how thick would you make the coating? (Assume that the index of refraction of the plane is higher than that of the coating.)

Thanks for ur help in Advance:)

Explanation / Answer

Given data:   a = slit width = 0.45 mm m = order of the fringe = 1 =  wavelength of the light = angle of diffraction distance between slit and screen is L = 2.06 m = 2060 mm The distance between the positions of zero intensity on both sides of the central bright fringe is   2y = 4.10 mm y = 2.05 mm ==> we know y = LTan if is very small tan = sin ==> sin = y/L = 2.05/2060
the condition for minima, a*sin = m -------- (1) 0.45 mm* 2.05/2060 = 1* ==> = 447.81 nm m = order of the fringe = 1 =  wavelength of the light = angle of diffraction distance between slit and screen is L = 2.06 m = 2060 mm The distance between the positions of zero intensity on both sides of the central bright fringe is   2y = 4.10 mm y = 2.05 mm ==> we know y = LTan if is very small tan = sin ==> sin = y/L = 2.05/2060
the condition for minima, a*sin = m -------- (1) 0.45 mm* 2.05/2060 = 1* ==> = 447.81 nm
* please post each question separately

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