Why are visible light waves critical for human vision?
**Poynting vector** S = E×B/μ₀ gives energy flow (W/m²), magnitude S = E B/μ₀, average = E₀ B₀/(2μ₀) = intensity, direction of propagation, showing energy transport perpendicular to E and B. Visible light waves have wavelengths that the human eye’s photoreceptors can detect, triggering neural responses that allow perception of color and detail in the environment. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Detectable wavelengths, illustrating EM wave transverse nature and Maxwell's displacement current concept.
Ref: NCERT > Physics Book > Electromagnetic Waves > Energy, Intensity and Momentum of EM Waves
