Dupla Fenda (Young)
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
y = mλL/d
About this calculator
The double-slit interference calculator, based on Young's experiment, determines the position of interference maxima in a fringe pattern. It uses the formula y = mλL/d, where y is the distance from the central maximum to the m-th order maximum, λ is the wavelength of light, L is the distance from the slits to the screen, and d is the slit separation. This tool is essential for students and professionals working with wave optics.
Young's double-slit experiment, performed in the early 19th century, demonstrated the wave nature of light. The calculator automates the calculation of bright fringe (maxima) and dark fringe (minima) positions, allowing you to visualize how constructive and destructive interference occurs. Simply input λ, L, d, and the desired order m to obtain the corresponding y position.
Use this calculator in physics labs, optical engineering projects, or academic studies. For example, when designing an experiment to measure the wavelength of a laser, you can vary d and L to predict where fringes will appear. Caution: ensure all units are consistent (typically meters) and that m is a positive integer for maxima (or half-integer for minima, if applicable).
Frequently asked questions
What does the order m mean in the formula?
The order m is an integer (0, 1, 2, ...) that indicates which interference maximum is being calculated. m=0 is the central maximum, m=1 is the first lateral maximum, and so on.
Can I use this calculator for white light?
Yes, but note that each wavelength (color) produces fringes at different positions. For white light, the pattern will be a superposition of colors, with a white central maximum and colored lateral fringes.
How do I convert units to use the formula?
Convert all measurements to meters. For example, if the wavelength is in nanometers, divide by 10^9; if the distance is in centimeters, divide by 100.
Does the formula work for minima (dark fringes)?
For minima, use y = (m + 0.5)λL/d, with m = 0, 1, 2, ... This gives the positions where destructive interference occurs.
What is the difference between interference and diffraction?
Double-slit interference results from the combination of waves from two coherent sources. Diffraction is the spreading of waves when passing through an aperture. In real experiments, both effects can occur simultaneously.