Question

In a single slit different 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

Answer: (B)

Narrower and brighter

Answer 2

The angular width of the central maximum is $2\lambda/a$ where a is the width of the slit. If the value of a is doubled the angular width of the central maximum decrease to half its earlier value this implies that the central maximum becomes much sharper. Furthermore if a sis doubled the intensity of the central maximum becomes four times thus the central maximum becomes four times thus the central maximum becomes much sharper and brighter.