How to use the thin film interference thickness calculator
Find minimum film thickness for constructive reflection. Enter wavelength in air, film refractive index in the fields above; the quarter-wave thickness, half-wave thickness are computed instantly and plotted on the chart so you can see how the answer changes.
Formula
Variables
- lam — Wavelength in air (nm)
- n — Film refractive index
Worked example
With wavelength in air = 550 nm, film refractive index = 1.38, the calculator gives quarter-wave thickness ≈ 99.63768 nm; half-wave thickness ≈ 199.2754 nm.
Frequently asked questions
What is the formula for the thin film interference thickness calculation?
Quarter-wave thickness (nm) = lam / (4 × n). Half-wave thickness (nm) = lam / (2 × n). Here lam is wavelength in air (nm), n is film refractive index.
What inputs do I need for the thin film interference thickness calculator?
You need wavelength in air in nm, film refractive index. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use this calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.