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Physics · Class 12

Single-slit diffraction

Wave Optics

Different parts of one aperture interfere. A narrow aperture spreads light more widely. The central maximum lies between the first minima and is twice the approximate width of each adjacent order interval.

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Single-slit diffraction

ஒரே பிளவின் வெவ்வேறு பகுதிகளின் அலைகள் குறுக்கீடு செய்கின்றன. பிளவு குறுகினால் மைய அதிகபட்சம் அகலமாகும்.

Key notes, relationships and model limits

Key relationship

I/Imax=(sin b/b)²; b=πay/(λD); central width≈2λD/a.

Remember

Different parts of one aperture interfere. A narrow aperture spreads light more widely. The central maximum lies between the first minima and is twice the approximate width of each adjacent order interval.

Common trap

Narrower openings make a broader far-field pattern, not a narrower one.

Model limits

Fraunhofer single-slit diffraction; uniform coherent illumination; small-angle screen coordinates. The b=0 limit is set analytically to1.

What you will learn

Distinguish single-slit diffraction from two-slit interference.

Try the experiment

Try both scenarios, change one control, and predict the result before checking the graph and readouts.

Think of it this way

Change one input while keeping the others fixed, as you would in a controlled experiment.

Worked example

At600 nm,a0.2 mm,D1 m, central width is6 mm.

Why this matters

The model connects single-slit diffraction with an observable reading. Check the equation and assumptions before applying it.

Before you start

SI units · algebra · graph reading

Check your understanding

Halving slit width changes central width to?

Read the explanation

The width is inversely proportional to a.

Course connection: Class XII Chapter 10. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.