Question

In single slit experiment, the width of the slit is reduced. Then, the linear width of the principal maxima ________

• A. increases but becomes less bright.
• B. decreases but becomes more bright.
• C. increases but becomes more bright.
• D. decreases but becomes less bright.

Answer 1

The correct option is A increases but becomes less bright.

Width of the central bright fringe is equal to $w=\frac{\lambda D}{d}$. Therefore, on reducing the width of the slit ($d$), linear width of the principal maxima increases. However, since the energy in central fringe remains the same, its intensity decreases and hence, it becomes less bright.