Any object or surface receiving light absorbs part of it: α [%] reflects part of it: ρ [%] may transmit part of it: τ [%] absorption α + ρ + τ = 100% reflection transmission
general selective
specular i r i = r C φ F i r T A C r i A T F φ C f f Figures by MIT OCW. CONCAVE CONVEX
specular spread diffuse Specular Spread Diffuse compound Diffuse/Specular Specular/Spread Diffuse/Spread Figures by MIT OCW.
Anodised aluminium White paint Plaster / white coating (new) Brushed aluminium Worn white coating White acoustical panels White tiling Light birch, ash, maple Pinewood (new) Ecru loth New concrete / light wood fiber (worn) Mahogany, walnut Light grey carpet Earthenware tiling, oak floor (worn) Red brick (bright and clean) Worn concrete Dark grey carpet 0.90 à 0.95 0.75 à 0.85 0.70 à 0.80 0.60 à 0.75 0.50 à 0.65 0.50 à 0.60 0.50 à 0.60 0.40 à 0.55 0.40 à 0.50 0.35 à 0.45 0.30 à 0.45 0.15 à 0.40 0.15 à 0.25 0.15 à 0.25 0.10 à 0.30 0.10 à 0.20 0.05 à 0.10 Very bright Bright Medium Dark Very dark
gloss and incidence reflection factor [%] incidence angle [ ]
gloss and incidence gloss level Figure by MIT OCW.
Transmission τ = τ d/d 0 0
Transmission regular spread diffuse mixed regular diffuse spread mixed Image courtesy of Prof. B. Paule, Estia SA, Lausanne, Switzerland.
Transmission regular spread diffuse mixed Figure by MIT OCW.
Transmission Refraction
Transmission i Air (n = 1) Refraction r Glass (n _~ 1.5) Snell-Descartes law i' n 1 sin i = n 2 sin r Air r' D Figure by MIT OCW.
Transmission Refraction Snell-Descartes law total reflection Air (n 2 ) Glass (n 1 ) Emerging Rays Ray Barely Emerging θ r i Total Reflection θ i θ i θ ic Incident at Critical Angle Figure by MIT OCW.
Transmission Refraction Polarization
Transmission Refraction Polarization Interference Figure by MIT OCW.
Transmission Refraction Polarization Interference Diffraction
Blackbody radiation Radiation only dependent on T Theoretical object small aperture in enclosure energy emitted is reabsorbed maximal power radiation compare practical sources Planck radiation law spectral radiance vs. λ and T Figure by MIT OCW. Radiant Power Output in Watts. M -2. µm -1 10 10 10 10 10 8 10 6 10 4 20,000 K A 10,000 K 3,000 K 2,000 K 1,000 K 10 8 10 6 10 4 500 K 10 2 B 10 2 10 100 1000 10,000 100,000 Wavelength in Nanometers Visible Region Watts. M -2. µm -1
Blackbody radiation Radiation only dependent on T Theoretical object small aperture in enclosure energy emitted is reabsorbed maximal power radiation compare practical sources Planck radiation law spectral radiance vs. λ and T Stefan-Boltzmann law radiated power per unit area = σ T 4
Image courtesy of Prof. B. Paule, Estia SA, Lausanne, Switzerland. Color temperature
Image courtesy of Prof. B. Paule, Estia SA, Lausanne, Switzerland. Color temperature
Image courtesy of Prof. B. Paule, Estia SA, Lausanne, Switzerland. Color temperature
Image courtesy of Prof. B. Paule, Estia SA, Lausanne, Switzerland. Color temperature
Image courtesy of Prof. B. Paule, Estia SA, Lausanne, Switzerland. Color temperature
Color temperature Color temperature and visible emission < 5500 K 5500 K > 5500 K Source requirements continuous spectrum color T 5500 K only fulfilled by daylight
Color temperature Color comfort E (Lux) 50000 20000 10000 5000 2000 1000 500 300 200 100 50 20 10 TOO "WARM" COMFORTABLE TOO "COLD" " Cold" color " Warm" color 1750 2000 2250 2500 3000 4000 5000 10,000 Tc (K) Figure by MIT OCW.