In a YDSE, slit separation is 3 mm, screen distance is 1 m and wavelength is 1 mm. Which pair gives (i) the distance of the first maximum from the central maximum and (ii) the total number of maxima on the screen?
Options

Question

In a YDSE, slit separation is 3 mm, screen distance is 1 m and wavelength is 1 mm. Which pair gives (i) the distance of the first maximum from the central maximum and (ii) the total number of maxima on the screen?

Options

G1 Physics · Accepted Answer

For exact geometry, maxima satisfy d sinθ=mλ. The first order has sinθ=1/3, so y=D tanθ≈0.3535 m=35.35 cm. Allowed orders satisfy |mλ/d|≤1, i.e. m=−2,−1,0,1,2 for finite screen positions in the source convention, giving 5 maxima. Hence option A.