Answer the following problems.

problem 1)a) Define and describe the terms:

i) Luminance.

ii) Illuminance.

b) Two isotropic point sources A and B are suspended at a height of 3m and 4m respectively above horizontal working plane. The luminous intensities are 1800Cd and 2000Cd respectively. What should be the distance between the lamps, so that the illuminance at point on the working plane directly below A is 75lux more than at the point directly below B?

c) Describe the terms Photopic, Scotopic and Mesopic visions in terms of lighting levels and photoreceptors. Draw appropriate sketches.

problem 2)a) What is incandescence? What is the importance of selecting tungsten as the filament material for incandescent lamps?

b) What do you mean by refraction? How is it significant for lighting applications?

c) What do you mean by thermal radiators? Draw the energy distribution curve of a black body radiator and describe it.

problem 3)a) Describe the halogen regenerative cycle? Mention the advantages of tungsten halogen lamps as compared to GLS incandescent lamps.

b) Describe the classification of luminaries with regards to symmetry of light distribution.

problem 4) Describe with neat sketches, the four basic techniques used for the measurement of photometric characteristics of a luminaire using Gonio photometer?