Practice question

**Infrared waves** λ≈700 nm to 1 mm, f≈10¹² to 4×10¹⁴ Hz, produced by hot bodies and molecular vibrations, wavelength range as per document 700 nm-1 mm, used in remote sensing because IR penetrates haze, thermal imaging detects IR emitted by objects, remote controls, effective for sensing temperature. Visible light ranges from about 4 × 10¹⁴ Hz to 7 × 10¹⁴ Hz , as stated in the document. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields 4 × 10¹⁴ Hz to 7 × 10¹⁴ Hz, illustrating EM wave transverse nature and Maxwell's displacement current concept.