Question

In a single slit diffraction experiment, the width of the slit is doubled. 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

The correct option is B narrower and brighter

The angular width of the entire central maximum is $\frac{2\lambda }{a}$, where $a$ is the width of the slit. If the value of $a$ is doubled, the angular width of the central maximum decreases to half its earlier value.
This implies that the central maximum becomes much sharper.
Furthermore, when $a$ is doubled, the intensity of the central maximum becomes four times. Thus, the central maximum becomes much sharper and brighter.

Hence, $\left(B\right)$ is the correct answer.