In a double-slit experiment,when both interference and diffraction are taken into account,which is the lowest order maximum that is missing in the case where the slit separations is 0.020 mm and the slit widths are each 0.005 mm?
A) 1
B) 2
C) 3
D) 4
E) no order is missing

Question

Quizplus · Accepted Answer

The positions of the maxima in a double-slit experiment are determined by the equation dsinθ = mλ, where d is the slit separation, λ is the wavelength of the light, θ is the angle between the incident light and the direction of the maximum, and m is the order of the maximum. The slit widths affect the intensity of the maxima but not the position.

The smallest order missing will occur when the distance between adjacent maxima is smallest. This occurs when sinθ is largest, which happens when θ = 90°. Solving the equation for m with these values gives m = d/λ = 20. Therefore, the first 20 maxima should be present. However, the width of the slits will cause some reduction in the intensity of these maxima, so the higher-order ones will be more difficult to observe. Answer D indicates that the fourth order is missing, which is reasonable given the small slit widths.

In a Double-Slit Experiment,when Both Interference and Diffraction Are Taken