# Explain why the central maximum in a single-slit diffraction pattern becomes wider when the width of the slit is decreased.

> IB DP Physics Standard Level (2023 syllabus) — C.3 Wave phenomena · Explain · 4 marks

## Mark scheme (4 marks)

1. Diffraction occurs as waves pass through the slit, causing the waves to spread out beyond the slit
2. The angle at which the first minimum occurs is given by sin θ ≈ λ/b, where b is the slit width
3. As slit width b decreases, the ratio λ/b increases, so the angle to the first minimum increases
4. The central maximum spans the region between the two first minima, so a larger angle to each first minimum means the central maximum is wider

## Key terms

- [diffraction](https://www.gradenine.co.uk/glossary/diffraction)
- [central maximum](https://www.gradenine.co.uk/glossary/central-maximum)

## Related

- [Revision notes for IB DP Physics Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-the-central-maximum-in-ef2897db) · Published by Druglandscape Ltd.