State any six factors on which efficiency of lighting depends.
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1) Level of illumination or degree of illumination: It depends on nature of work to be carried out. The degree of level of illumination also depends on following factors. i) The size of object & its distance from observer. ii) If object is moving speedly higher level of illumination is required than stationary object. iii) If the objects are required to be seen for long duration of time, higher level of illumination is necessary & for stair cases, corridors less illumination is required. 

2) Glare: The glare causes unnecessary eye fatigue so it must be avoided, it can be prevented by using diffusing glass screen, suitable reflectors & proper mounting height. Reflected glare from the polished surfaces within the line of vision should be avoided. 

3) Shadows: The formation of long and hard shadows must be avoided. The long and hard shadows cause accident. Such shadows can be avoided by i) Using proper mounting height of the lamps. ii) Using more number of lamps & providing indirect lighting. iii) Employing wide surface sources of light. Complete absence of shadows is again not recommended as soft shadows are required to identify three dimensional objects. 

4) color rendering: This refers to the ability of the light source to reproduce the original colour of the objects when the object is illuminated by that source. 

5) Lamp fittings: The lamp fittings serve the following functions in good illumination scheme. i) To diffuse the light ii) To cut off the light at certain angle to avoid glare iii) To give mechanical protection to light source. iv) To increase the aesthetical requirement of the premises. V) To control the level of light (control gear)

6) Maintenance: Regular cleaning of lamps & light fittings is necessary to maintain their efficiency. The maintenance is necessary against dust, water leakage, dangerous gases which may cause corrosion of light fittings. Hence light fittings should be simple & easy from maintenance point of view. 

7) Following factors are considered while designing interior illumination: utilization factor, deprecation factor, Maintenance factor and space to height ratio.


1. Comfortable: - The energy illumination scheme should be comfortable to everybody. 

2. Pleasant surrounding: By the electrical lighting or the electrical illumination scheme the surrounding area of that location should be pleasant. 

3. Long Life: - The life of the designed illumination should be larger. 

4. Economy: - The cost of the designed illumination scheme should be low. 

5. Less maintenance: - For any type of illumination scheme the maintenance & repairing should be less. 

6. Appearance: - The appearance of illumination scheme should be good. 

7.less glares: - The glare is fatigue to the human eyes. The illumination scheme is designed is such a way that there should be less glare to everyone i.e. Only electrical & mechanical accidents will be less. 

8. less Flickers: - The flicker is change in light intensity. This flicker should be always less for any type of illumination scheme. In the flicker there are change of stroboscopic effect at the time of workshop lighting in it is very important. 

9. To avoid hard Shadows: - The whole illumination scheme is designing for minimum shadows. At the time of flood light the hard shadows are avoided. 

10. Sufficient lux Level: - The lux level is decided by the type of application, type of location.

11. Cleanliness: - The illumination scheme should be free from any type of ash, smoke or any other air pollution it should be clean. 

12. Simple Control: - The illumination scheme designed by the electrical lighting is very simple. The control, multicolour light intensity control is also possible in electrical illumination.


1. Stroboscopic Effect: Stroboscopic effect should be less 2. Area of working Plane: Number of lighting devices depends upon area of working plane 3. Quality of civil construction works: Waste light factor, utilization factors depends upon quality of civil construction work. 4. Height of lamp fitting: Lighting efficiency depends upon space to height ratio. 5. Type of lighting source: There are number of lighting source having different illumination efficiency, So lighting efficiency depends upon this type lighting source. 6. Diffusion factor: By this factor the actual required lux level on working plane is decided. 7. Distribution of lux on working plane: The lux level on working plane should be uniformly distributed.


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