Two light sources against a wall

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The problem involves calculating the distance from the center point on a wall to the 10th bright spot created by two light sources positioned 0.5 mm apart, with a wavelength of 550 nm, at a distance of 50 cm. The formula used is x = nLv/d, leading to an initial calculation of 5.5 mm for the distance. The reasoning includes the assumption that the angle is small enough for the approximation to hold. A more precise calculation using the exact formula results in a value of 5.5003 mm. The discussion confirms the accuracy of the calculations and the assumptions made.
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Homework Statement



Two light sources half a millimetre apart with a wavelength of 550nm shine on a wall exactly 50cm away. What is the distance between the centre point on the wall and the 10th bright spot out?

Homework Equations



x=nLv/d


The Attempt at a Solution



x=10x0.5x(5.5x10^-7)/0.0005
= 0.0055m = 5.5mm
 
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I agree with that answer. The assumption that the angle is sufficiently small so that nλ = d*sin(θ) equals dx/L appears to be reasonable. Working it out with the exact nλ = d*sin(θ) yields x = 5.5003 mm.
 

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