Why are infrared waves used in thermal imaging devices?
**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. Infrared waves are emitted by objects proportionate to their temperature, allowing thermal imaging devices to detect and map these emissions as temperature variations. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Their temperature relation, illustrating EM wave transverse nature and Maxwell's displacement current concept.
Ref: NCERT > Physics Book > Electromagnetic Waves > Infrared, Visible Light and Applications