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

Answer: (B)

narrower and brighter

The angular width of the central maximum is given by:

$2D\lambda /a$ 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. Due to this, the intensity of the central maximum will be increased to four times.

This implies that the central maximum becomes much sharper. Thus the central maximum becomes much narrower and brighter.