A light bulb turns electrical energy into light and heat. Which output is the wasted one?

1. A system takes in input energy and gives out output energy. 2. The output we actually want from a bulb is light. 3. The heat it also gives off is not wanted, so it is the wasted output. 4. A bulb makes no sound worth counting, so that option is not an output at all. _Source: Siyavula Natural Sciences Grade 7 (CC BY 4.0), Useful and wasted energy_