Core identity (vacuum/air):
c = λ ν ⇒ ν(λ) =c / λ, λ(ν) =c / ν
where
c = 299 792 458 m s^ −1
λ lambda = wavelength (m), ν nu = frequency (Hz).
1) Function view (solve as mappings)
a) Frequency as a function of wavelength
ν(λ) = c / λ
* λ = 400 nm⇒ ν ≈ 7.4948 × 10^14 Hz
* λ = 500 nm⇒ ν ≈ 5.9958 × 10^14 Hz
* λ = 650 nm⇒ ν ≈ 4.6122 × 10^14 Hz
b) Wavelength as a function of frequency
λ(ν) = c / ν
* ν = 100 MHz ⇒ λ ≈ 2.9979 m
* ν = 1.0 GHz ⇒ λ ≈ 0.29979 m
* ν = 2.4 GHz ⇒ λ ≈ 0.12491 m
2) Medium shift (refractive index n)
Phase speed drops to v = c / n. Frequency stays the same when crossing media; wavelength contracts:
λ_medium = v / ν= c / n ν=λ_0 / n
Example: λ_0 =500 nm in vacuum, glass (approx. n ≈ 1.5 )
⇒ λ_glass ≈ 500 / 1.5 = 333.3 nm, νnu unchanged ≈ 5.9958×10^14 Hz.
Dispersion note: n = n (λ)n. In many media nn gently decreases with increasing λ (normal dispersion), so v(λ) and λ_medium are wavelength-dependent.
3) Angular forms & wavevector
ω = 2πν , k = 2π / λ
Vacuum dispersion gives ω=c k (phase velocity v_p = ω / k = c ).
Example at λ = 500 nm:
* ν ≈ 5.9958×10^14 Hz
* ω ≈ 3.7673×10^15 rad s^−1
* k ≈ m1.2566×10^7 rad m^−1
In dispersive media: ω = c / n(λ) {k} , k , and group velocity v_g = dω / dk may differ from v_p.
4) Energy link (for photons)
E = hν = hc / λ , h = 6.62607015 × 10^−34 J s
λ = 500 nm ⇒ E ≈ 3.9729 × 10^−19 J ≈ 2.480 eV.
5) Story grafts (how Strange “solves” in three modes)
Light-mode (wave-front alignment): Collapse a swarm of possibilities by fixing ν(λ) =c / λ and locking a single (ω , k) pair so ω = ck. (She whispers the frequency to still the glare.)
Dark-mode (trust the metric):
Move by invariant ν through media:
λ ↦ λ /n while ν holds—she navigates void by counting primes as steps of constant ν.
Shadow-mode (balance):
Blend phase and group motion: choose k from geometry, ω from intent, then test causality with v_g = dω/dk. If v_g strays, she “seasons” n (λ) (i.e., changes medium) to restore safe passage.
6) Quick “function cards” for later insertion
Frequency law: ν(λ) = c / λ
Wavelength law: λ(ν) = c/ ν
Angular pair: (ω , k) = (2πν, 2π / λ)
Vacuum dispersion: ω=ck
Photon energy: E = hc / λ= hν
Keep-by for Chapter margins: “If the bowl is frequency, the bridge is wavelength; if the verse changes medium, keep ν and let λ bend.”