---
title: "Monochromatic laser light of wavelength \\(\\lambda\\) is incident on a single slit of adjustable width \\(a\\). The resulting diffraction pattern is observed on a screen placed a fixed distance \\(D\\) from the slit. If the slit width \\(a\\) is decreased while remaining larger than \\(\\lambda\\), how does the width of the central bright fringe on the screen change, and why?"
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url: "https://nerd-notes.com/ubq/116608/"
date_modified: "2026-08-04T05:25:12+00:00"
---

# Monochromatic laser light of wavelength \(\lambda\) is incident on a single slit of adjustable width \(a\). The resulting diffraction pattern is observed on a screen placed a fixed distance \(D\) from the slit. If the slit width \(a\) is decreased while remaining larger than \(\lambda\), how does the width of the central bright fringe on the screen change, and why?

Monochromatic laser light of wavelength \(\lambda\) is incident on a single slit of adjustable width \(a\). The resulting diffraction pattern is observed on a screen placed a fixed distance \(D\) from the slit. If the slit width \(a\) is decreased while remaining larger than \(\lambda\), how does the width of the central bright fringe on the screen change, and why?

- **A.** It decreases because a narrower slit restricts the light beam, causing it to cover a smaller area on the screen.
- **B.** It decreases because the wavelength of light decreases as it passes through a narrower aperture.
- **C.** It remains unchanged because the distance to the screen and the wavelength of the light are kept constant.
- **D.** It increases because the angular spread of the diffracted light is inversely proportional to the slit width.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/116608/*