Fringe width
Intermediate
Spacing between adjacent bright fringes.
β = λD/dβ = λD/d: fringes are wider for longer wavelengths, larger screen distances and closer slits. In water β reduces by n.
Red fringes are wider than blue.
Measure over several fringes to reduce error.
In more detail
The fringe width in Young's experiment is β = λD/d, where λ is the wavelength, D is the distance to the screen and d is the slit separation. Fringes are evenly spaced.
Real-world uses
- Measuring wavelengths of light with a double slit.
- Designing interference filters with controlled fringe spacing.
- Engineers measuring a laser's wavelength use the spacing between fringes, which is set by the slit separation and the screen distance.
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Frequently asked questions
How can I make fringes wider?
Increase the wavelength or the screen distance, or decrease the slit separation.
Why are fringes equally spaced?
Because for small angles, path differences change linearly with position.
How can I make the fringes wider?
Increase the distance to the screen or the wavelength, or decrease the slit separation.
Related topics in Optics
Huygens' principle · Coherent sources · Young's double slit · Intensity in interference · Thin film interference · Newton's rings