1.Why it the tungsten–halogen lamp more efficient than a normal tungstenfilament
lamp?2. Explain in simple terms how electromagnetic radiation is emitted from a lowpressure gas or vapour when an electric current is flowing in it. Indicate how current can flow in the gas or vapour. 3.Why is a ballast needed for the operation of a discharge lamp? Explain why a
ballast used will be more efficient if it takes the form of choke rather than a resistor.