Which type of waves is utilized in the night vision equipment?
Infrared waves used in night vision, thermal detection, longer wavelength than visible.
Ref: NCERT Physics Class 12 Chapter 10 Wave Optics
#thermal imaging
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What is a common method to detect infrared waves as per the document?
**Aerials produce radio waves** by rapid acceleration/deceleration of electrons in antenna driven by AC, frequency equals driving frequency, for 60 MHz, λ=c/f=3×10⁸/60×10⁶=5 m, half-wave antenna length λ/2=2.5 m, efficient radiation when antenna size comparable to λ. The document lists thermopiles, bolometers, and infrared photographic film as detectors for infrared waves. Bolometers are a common choice. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Bolometers, illustrating EM wave transverse nature and Maxwell's displacement current concept.
Ref: NCERT > Physics Book > Electromagnetic Waves > Production of EM Waves and Hertz Experiment
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, ill
Ref: NCERT > Physics Book > Electromagnetic Waves > Infrared, Visible Light and Applications
Why are infrared detectors used in Earth satellites?
**IR effectiveness in remote sensing** because IR scattered less than visible by atmosphere, can detect heat signatures, used in satellite imaging for vegetation, moisture, military night vision, illustrating application based on thermal emission and low scattering. Infrared detectors are used for military purposes and to observe crop growth, 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 For military purposes and crop observation, illustrating EM wave transverse nature and Maxwell's displacement current concept.
Ref: NCERT > Physics Book > Electromagnetic Waves > Infrared, Visible Light and Applications
Why are infrared waves often associated with thermal imaging?
**IR effectiveness in remote sensing** because IR scattered less than visible by atmosphere, can detect heat signatures, used in satellite imaging for vegetation, moisture, military night vision, illustrating application based on thermal emission and low scattering. Infrared waves are emitted by objects based on their temperature, and detectors can sense these emissions to map temperature variations, making them ideal for thermal imaging. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Temperature-dependent emission, illustrating EM wave transv
Ref: NCERT > Physics Book > Electromagnetic Waves > Infrared, Visible Light and Applications
