(2) infra-red rays Explanation: When electricity is passed through the filament, the filament gets hot. Depending on the temperature of the filament, radiation is emitted from the filament. The filament's temperature is very high, generally over 2,000°C. At this high temperature of 2,000°C, about 5 percent of the electrical energy converts into visible light and rest of it is emitted as heat or infrared radiation.