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

all of the above

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