seeing is a kind of action & if something is used for an action then that something produces the things required for that action ->  if something is used for seeing then that something produces the things required for seeing  if something is used for seeing then that something produces the things required for seeing & a light bulb is used for seeing in the dark ->  a light bulb that is used for seeing in the dark produces the things required for seeing  a light bulb that is used for seeing in the dark produces the things required for seeing & seeing requires light energy ->  the light energy produced by the light bulb is used for seeing  the light energy produced by the light bulb is used for seeing & an incandescent light bulb converts electrical energy into light energy and heat energy & the heat energy produced by the light bulb is not used ->  the light bulb converts electrical energy partially to heat energy that is not used  electrical energy is a kind of energy & energy is a kind of resource ->  electrical energy is a kind of resource  the light bulb converts electrical energy partially to heat energy that is not used & electrical energy is a kind of resource ->  the light bulb converts a resource partially to heat energy that is not used  the light bulb converts a resource partially to heat energy that is not used & if something converts a resource into energy it doesn't use then that something is not using that resource efficiently -> the light bulb does not use the resource efficiently becasue it produces heat energy that is not used