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In a single-slit diffraction setup, if the slit width is increased to twice its initial value, what happens to the central bright fringe of the diffraction pattern?

1. It becomes narrower and less intense
2. It becomes narrower and more intense
3. It becomes wider and less intense
4. It becomes wider and more intense

Correct answer: It becomes narrower and more intense

Solution

Central maximum angular half-width = lambda/a, so doubling slit width a halves the width (narrower). A wider slit admits more energy, so the central fringe also becomes more intense: narrower and more intense.

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