Light & Optics Labλ = c / f • E = hf

400 nm to RGB & Color Calculator

Approximate how 400 nm monochromatic spectral light can be represented in sRGB, and calculate CIE 1931 tristimulus values, THz frequency, and photon energy.

CIE 1931 Spectral Synthesis
400 nm
Violet
#5B00D3
nm
380 nm (Violet)555 nm (Peak)750 nm (Deep Red)
Frequency
749.481 THz
Photon Energy
3.1 eV
sRGB Channels
91, 0, 211
CIE 1931 XYZ
0.0115, 0.0013

Why You See This Color (400 nm)

At 400 nm, monochromatic light stimulates human Short-wavelength (S) retinal cone photoreceptors with minimal activation of Medium (M) and Long (L) cones. The brain interprets this high-frequency electromagnetic stimulus (approximately 749.481 THz, carrying 3.1 eV per quantum photon) as deep violet. Because the eye's photopic luminous efficiency V(λ) drops sharply toward the near-ultraviolet threshold, this wavelength requires greater radiant flux to match the perceived brightness of green light.

Physical Parameter Breakdown

Wavelength (λ):400 nm (400 × 10⁻⁹ m)
Oscillation Frequency (f):749.481 THz
Photon Quantum Energy (E):3.1 eV
CIE 1931 Tristimulus (XYZ):X:0.0115 Y:0.0013 Z:0.0608
Traian Anghel
Traian AnghelAuthor & Reviewer

Physics Teacher & Educational TechnologistBrăila, Romania

Last Reviewed: August 2026
Wave Lab calculators are constructed using rigorous peer-reviewed physics formulas from verified metrological repositories. Every equation, spectral conversion, and acoustic property is tested against NIST, CIE, and ISO datasets.
Verified Sources:NIST CODATACIE 1931 2° ObserverNASA Glenn Research

Enjoy Wave Lab? Follow us on Google

Add wavelab.tools as a Preferred Source so our calculators and physics guides show up first in Google Search, Top Stories, AI Overviews and Discover.

Add as a preferred source on Google

Related Physics Calculators