Halliday, Resnick & Walker — Interference: Problem 56

56 In the double-slit experiment of Fig. 35-10, the viewing screen is at distance \(D = 4.00 \text{ m}\), point \(P\) lies at distance \(y = 20.5 \text{ cm}\) from the center of the pattern, the slit separation \(d\) is \(4.50 \mu\text{m}\), and the wavelength \(\lambda\) is \(650 \text{ nm}\). (a) Determine where point \(P\) is in the interference pattern by giving the maximum or minimum on which it lies, or the maximum and minimum between which it lies. (b) What is the ratio of the intensity \(I_P\) at point \(P\) to the intensity \(I_{cen}\) at the center of the pattern?