Beer's Law & Spectrophotometry Simulator
Shine light through a virtual cuvette. Change the concentration, path length, and molar absorptivity to see how absorbance (A = εbc) and transmittance respond, then use a calibration curve to find an unknown.
Want the concepts first? Read the Beer–Lambert law lesson.
Measured at λmax ≈ 525 nm, the wavelength this solution absorbs most strongly.
Absorbance, A
0.480
Transmittance, %T
33.1%
A = εbc = 2400 × 1.0 × 2.00e-4 = 0.480
%T = 10−A × 100 = 33.1%
Light path
Calibration curve
Five standards measured with the current ε and b. The slope of A vs. c equals εb = 2400 M⁻¹.
c = A ÷ (εb) = 0.45 ÷ 2400 = 1.88e-4 M
AP FRQ traps
- Water droplets or fingerprints on the cuvette scatter light → measured A is too high → calculated concentration is too high.
- Rinsing the cuvette with water and leaving it wet dilutes the sample → A too low → concentration too low.
- Measure at λmax: absorbance changes most with concentration there, giving the most sensitive calibration.
- Absorbance has no units; ε has units of M⁻¹cm⁻¹ so that εbc is unitless.