Difração Fenda Simples
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
sen θ = mλ/a
About this calculator
This single-slit diffraction calculator determines the angular position of intensity minima in the diffraction pattern. Diffraction occurs when a wave passes through a narrow opening, spreading beyond the straight-line path. For a slit of width a, the condition for minima is given by sin θ = mλ/a, where θ is the angle relative to the central axis, m is the order of the minimum (m = ±1, ±2, ...), λ is the wavelength of light, and a is the slit width.
The calculator uses this formula to compute the angle θ for a given wavelength and slit width, or vice versa. You can input three of the four parameters (λ, a, m, θ) and obtain the fourth. This is useful in optics labs, spectroscopy projects, or educational experiments to verify the wave theory of light.
Use this tool when you need to analyze diffraction experiments, such as measuring slit width from the observed pattern or predicting minimum positions for a known setup. Ensure consistent units (meters for a and λ, radians or degrees for θ).
Caution: the formula is valid only for small angles (paraxial approximation) and for long rectangular slits. For larger angles, the approximation sin θ ≈ θ is not accurate. Also, single-slit diffraction does not consider multiple-slit interference effects (as in diffraction gratings).
Frequently asked questions
What does negative m mean in the formula?
Negative m indicates minima on the opposite side of the central axis. The diffraction pattern is symmetric, so m = -1, -2, ... correspond to negative angles.
Can I use this calculator for sound waves?
Yes, single-slit diffraction applies to any wave type, including sound, as long as the slit width is comparable to the wavelength.
What is the difference between diffraction and interference?
Diffraction is the spreading of waves passing through an aperture, while interference is the superposition of waves from multiple sources. This calculator deals only with single-slit diffraction.
Why does the formula use sine and not tangent?
The minimum condition is derived from the path difference between rays from different points in the slit, which is a sin θ. For small angles, sin θ ≈ tan θ, but the exact formula uses sine.
What happens if the slit width is much larger than the wavelength?
The angles of minima become very small, and the diffraction pattern contracts, approaching straight-line propagation (geometric optics).