Hair Diffraction Calculator
Estimate hair diameter using the single-slit diffraction approximation.
How to Use This Calculator
Measure fringe spacing
Shine a laser through a single hair onto a wall. Measure distance between adjacent minima (dark bands).
Measure screen distance
Measure the distance from the hair to the wall or screen.
Enter laser wavelength
Common red laser ≈ 650 nm, green ≈ 532 nm, He-Ne ≈ 632.8 nm.
Formula
a \u2248 (\u03BB L) / s
Where: a is hair diameter, \u03BB is laser wavelength, L is distance to screen, s is fringe spacing.
Example: \u03BB = 633 nm, L = 2 m, s = 2 mm → a ≈ 0.000633·2/0.002 = 0.633 mm = 633 µm.
About Hair Diffraction Calculator
A single hair acts like a fine obstacle, producing a diffraction pattern similar to a single slit. Measuring the spacing allows estimating hair thickness.
Tips
- Use a stable mount for the hair and laser.
- Measure several spacings and average to reduce error.
- Darken the room for clearer fringes.
Frequently Asked Questions
Why use single-slit approximation?
A thin obstacle produces a pattern equivalent to a slit of similar width due to Babinet’s principle.
How accurate is this method?
Typically within 10–20% with careful measurement. Multiple trials improve accuracy.
Which fringe spacing should I measure?
Measure the distance between adjacent dark minima near the center for best precision.