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Architecture Lighting Design & Acoustics

Architecture Lighting Design & Acoustics. The illuminance on a surface which is produced by a single light source, varies inversely as the square ofthe distance from the source. This is known as the INVERSE SQUARE LAW and is shown by the expression:.

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Architecture Lighting Design & Acoustics

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  1. Architecture Lighting Design & Acoustics

  2. The illuminance on a surface which is produced by a single light source, varies inversely as the square ofthe distance from the source. This is known as the INVERSE SQUARE LAW and is shown by the expression: If the distance is doubled between the light source and surface, the illuminance E will fall to one quarter of the previous value. Although the illuminated area will increase in size, the illuminance on the surface however will decrease accordingly. This effect can be demonstrated by shining a torchlight directly onto a flat surface and observing the increased area of light when the torch is moved further away from the surface.

  3. INVERSE SQUARE LAW

  4. Laws Of Illumination

  5. COSINE LAW If a beam of light from a lamp hits a surface at an angle, the illuminated area increases but the illuminance on the surface is lower than when the light is pointed directly at the surface. This effect can be demonstrated by holding a torchlight at an angle to a surface, rather than directly at the surface, and observing the increased illuminated area. The illuminance at a point on the surface will now be reduced by a factor of the cosine of the angle. This is known as the COSINE LAW and is shown by the expression:

  6. COSINE LAW

  7. COSINE LAW The COSINE LAW is illustrated in the Figure. A 500 cd incandescent lamp is fixed at a height of 2 metres directly above a long bench, and the value of illuminance at point P is to be determined.

  8. COSINE LAW Figure shows two luminaires, LI and L2, mounted 5 metres apart. Each lamp inside the luminaires emits 600 cd in all directions. The values of illuminance at points PI, P2 and P3 are to be determined..

  9. COSINE LAW

  10. COSINE LAW

  11. COSINE LAW

  12. COSINE LAW

  13. COSINE LAW

  14. COSINE LAW Example twoThe forecourt of a building is to be illuminated by four floodlights , mounted on 6 meter high poles. A pole is positioned at each corner of the square forecourt which measures 20 m x 20 m. Each lamp and luminaire combination produces a luminous intensity of2500 cd. Illuminance levels . are to be determined at: - (a)' the base of each pole, P1 (b) the centre of the forecourt, P2 (c) a point on the ground midway between each pole, P3

  15. COSINE LAW

  16. COSINE LAW

  17. COSINE LAW

  18. COSINE LAW To determine distance dl, distance bl must be calculated first

  19. COSINE LAW

  20. COSINE LAW To determinedistance d1, distance b1 must be calculated first

  21. COSINE LAW

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