Mainly heat.
Electrical goes in. Electromagnetic (heat and light) come out.
The Sun.
From the electric current that powers it.
Because efficiency is measured in Output/input. At the same light bulb output, one with lesser energy input required is higher in efficiency. Possible confusion come from description of low energy light bulb without stated the high or low energy is compared at what lux it can produce light.
The energy for a light bulb typically comes from electricity flowing through the filament, which heats up and produces light. The electricity is usually supplied by power plants that generate electricity through various means such as burning coal, natural gas, or using renewable sources like wind or solar.
Electrical goes in. Electromagnetic (heat and light) come out.
In a flashlight, energy comes from the batteries. The batteries provide electrical energy to power the light bulb or LED in the flashlight, producing light as a result.
"60 watts" means "60 joules every second". That's what a '60 watt' bulb is designed to consume. If you put 100 joules of energy into a light bulb, 100 joules of energy are going to come out of it, one way or another. Either that energy will be converted into light and heat by the bulb's filament, or else it won't get consumed at all, and it'll come out the other side of the bulb and still be available for use in some other device. So, comparing output energy to input energy is not an effective way to evaluate the efficiency of a light bulb. What you need to do, in order to compare the economy and effectiveness of light bulbs, is to compare LIGHT output to input ENERGY.
Energy comes from various sources like the sun, fossil fuels, and nuclear reactions. It is transformed into different forms such as heat, light, and mechanical energy and is used to power various processes in our daily lives. Eventually, most of the energy is dissipated as waste heat into the environment.
The energy delivered to a light bulb in a closed circuit with a battery comes from the chemical reactions happening inside the battery. These reactions create an electric current that flows through the circuit and powers the light bulb.
The electric power measured in watts is used to heat a filament in the light bulb (which glows because it is very hot). More energy gives more heat. It's very simple.
Remove the light bulb connector from the light. Take hold of the light bulb, push in and turn at the same time. The light bulb will come out. Reverse the process to install the new light bulb.