Wave equation.

λ = c / ν (equivalently c = λν)

• λ (lambda) — wavelength (peak-to-peak distance), typical units µm (1 µm = 10⁻⁶ m).
• c — speed of light, 3 × 10⁸ m/s.

• ν (nu) — frequency, Hz (cycles per second).

• Key takeaway: wavelength and frequency are inversely related. Long wavelength ↔ low frequency ↔ low energy (see slide 9).