Question

In a single slit diffraction experiment, the width of the slit is made double its original width. Then the central maximum of the diffraction pattern will become
A. narrower and fainter
B. narrower and brighter
C. broader and fainter
D. broader and brighter

Answer 1

Correct Answer - B
The angular width of the central maximum is `2lambda//a` where a is the width of the slit. If the value of a is doubled, the angular width of the central maximum decreases to half its earlier value. This implies that the central maximum becomes much sharper. Furthermore if a is doubled, the intensity of the central maximum becomes four times. Thus the central maximum becomes much sharper and brighter.