三类视锥与同色异谱

The eye keeps three numbers

The response is a projection

Matching with three primaries

Metamers

Two lights have very different spectra, one spiky and one smooth, yet they look identical to a human observer. What is the correct explanation?

A display must reproduce the appearance of an arbitrary light using mixtures of three fixed primaries. Why does the cone projection guarantee this is possible in principle?

A simplified cone has sensitivities $(0.5, 0.2, 0.0)$ across three sampled wavelengths, and an incoming spectrum has intensities $(10, 20, 30)$ at those samples. Write the cone's response as a number.