increasing the mounting height of the lamp
using diffusers
using reflectors to cut-off the light at certain angle
all of the above
avoid glare
provide better illumination
protect the lamp
depreciation in the capital cost of the installation
effects of dust, dirt and types of lamps used
effects of dust, dirt and fall in light-output of the lamp during its life
condition of the room and the type of lamp used
NTC thermistor
PTC thermistor
Voltage dependent resistor
Flasher
To break and make the circuit but it gives no light
To break and make the circuit and it gives light
To break the circuit only but gives no light
To make the circuit only and also gives light