Single Slit Diffraction Calculator
Enter slit width a and wavelength λ in metres, screen distance L in metres, and fringe order m (a positive integer).
A QUICK WALKTHROUGH
How to use this tool
- Enter a, λ, L and a positive integer order m in metres.
- Calculate y≈Lmλ/a and the central width 2Lλ/a.
- Use the estimate only in the far-field small-angle regime.
Model and limits
Dark fringes satisfy a sin(θ)=mλ. This calculator reports y≈Lmλ/a and central width 2Lλ/a using sin(θ)≈tan(θ)≈θ. Orders with mλ>a are impossible and rejected.
GOOD TO KNOW
Common questions
What is the central maximum width?
The small-angle estimate is 2Lλ/a, from the first dark fringe on each side.
Does this work at large angles?
No. Screen position is approximated using the far-field small-angle relation.