Two coherent microwave point sources of wavelength λ are separated by 5λ. Interference is observed on the line through one source perpendicular to the source separation. For λ=4 mm, which set gives the positions of maxima from the source along the observation line, as listed in the source answer?

Question

G1 Physics · Accepted Answer

At a point x on the observation line, path difference is √[x²+(5λ)²]-x. Setting this equal to mλ and solving x=[25-m²]λ/(2m) for allowed positive m gives 48, 21, 32/3, 9/2 and 0 mm for λ=4 mm. Hence option A.