Correct Answer - Option 3 : 1.5
Concept:
Depreciation factor:
- Depreciation factor is defined as the ratio of the illumination when everything is clean to illumination under normal working conditions.
- Due to the accumulation of the dirt, dust, and smoke on the lamps they emit less light as compared to when they are new.
- Similarly, walls and ceilings reflect less light when are covered with dust. Hence to design a source of light we need to consider the depreciation factor.
- It is usually greater than 1.
Calculation:
Given that
illumination under normal working condition = 400 lux
illumination after cleaning = 600 lux.
Depreciation factor = 600 / 400 = 1.5
