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Normal Incidence Fresnel Reflectance Calculator
Calculate intensity reflectance at normal incidence between lossless dielectrics. Choose input units and calculate one value within the stated conditions.
Inputs
Calculations run in this browser. Scientific notation such as 1.2e-3 is supported. Do not group thousands.
Result
Intensity reflectance R
Enter values and select Calculate.
R = ((n₁−n₂)/(n₁+n₂))²
Assumptions
Required: positive real refractive indices and normal incidence at a nonmagnetic nonabsorbing planar interface. This is intensity reflectance, not amplitude reflection. Thin films, absorption and oblique incidence are excluded.
Displayed values are floating-point approximations. Design safety factors and unprovided error contributions are not calculated.
Formula references and credits
NaNa Lab created the code, descriptions, icons and preview images. Text, figures and code from the linked references have not been reproduced.
Physical constants: NIST / CODATA 2022. The values of μ₀ and ε₀ are measured recommendations, not exact defining constants. Values and precision notes are in the source record.
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