Interaction of light and matter

Transcription

1 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

2 general selective

3

4 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

5 specular spread diffuse Specular Spread Diffuse compound Diffuse/Specular Specular/Spread Diffuse/Spread Figures by MIT OCW.

6 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 à à à à à à à à à à à à à à à à 0.10 Very bright Bright Medium Dark Very dark

7 gloss and incidence reflection factor [%] incidence angle [ ]

8 gloss and incidence gloss level Figure by MIT OCW.

9 Transmission τ = τ d/d 0 0

10 Transmission regular spread diffuse mixed regular diffuse spread mixed Image courtesy of Prof. B. Paule, Estia SA, Lausanne, Switzerland.

11 Transmission regular spread diffuse mixed Figure by MIT OCW.

12 Transmission Refraction

13 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.

14 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.

15 Transmission Refraction Polarization

16 Transmission Refraction Polarization Interference Figure by MIT OCW.

17 Transmission Refraction Polarization Interference Diffraction

18 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 ,000 K A 10,000 K 3,000 K 2,000 K 1,000 K K 10 2 B , ,000 Wavelength in Nanometers Visible Region Watts. M -2. µm -1

19 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

20 Image courtesy of Prof. B. Paule, Estia SA, Lausanne, Switzerland. Color temperature

21 Image courtesy of Prof. B. Paule, Estia SA, Lausanne, Switzerland. Color temperature

22 Image courtesy of Prof. B. Paule, Estia SA, Lausanne, Switzerland. Color temperature

23 Image courtesy of Prof. B. Paule, Estia SA, Lausanne, Switzerland. Color temperature

24 Image courtesy of Prof. B. Paule, Estia SA, Lausanne, Switzerland. Color temperature

25 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

26 Color temperature Color comfort E (Lux) TOO "WARM" COMFORTABLE TOO "COLD" " Cold" color " Warm" color ,000 Tc (K) Figure by MIT OCW.