LIGHT is just an electromagnetic wave with certain freequency limit... IF A CHARGE IS STATIONARY...ONLY ELECTRIC
FIELD IS PRODUCED......IF CHARGE IS MOVING AT CONSTANT SPEED.......ONLY MAGNETIC FIELD IS PRODUCED...........................
when change in electric field is occur......change in magnetic field occurs.....means electro - magnetic wave (light) is produced
when we switch on the bulb electrons move with CONSTANT ACCELARATION( VARYING SPEED).......thus EM waveof
certain freequency(light) is produced..... when we switch off the bulb...... electrons move with CONSTANT
RETARDATION......and finally end at rest......so....EM wave don't produced..........
produced