# Double Slit Diffraction

by foxx0775
Tags: diffraction, fringes, maximum, minimum, slits
 P: 1 1. The problem statement, all variables and given/known data A parallel beam of mono-chromatic light (500nm) is incident on 2 long narrow slits: slit width is 0.1mm and the distance between slit centres is 0.3mm. a) How many bright fringes cover the central diffraction maximum? 2. Relevant equations Condition for constructive interference: $$\Delta = 2d.cos\theta = 2m(\lambda\div2)$$ Reduces to: $$2d=m\lambda$$ as $$cos\theta=1$$ ? 3. The attempt at a solution I get 1200 once I convert both$$d$$and $$\lambda$$ into metres. Is this the right thing to do? I'm not sure this is the amount that cover the central maximum, what does this bit mean? - - - Part b) 1. The problem statement, all variables and given/known data Part b) Calculate the angle corresponding to the first diffraction minima 2. Relevant equations $$sin\theta= ((2m-1)\lambda)\div2)\div d$$ 3. The attempt at a solution Taking m as 1 because it is the first diffraction minima Reduces to: $$\theta = arcsin[ (5\times10^{-7}) / (6\times10^{-4}) ]$$ I get $$\theta$$ = 0.048 degrees is this correct? There is part c) but haven't attempted it yet, overall the whole question is allocated 14 marks. 1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution