The major difference between an incandescent 40-watt light bulb and a 60-watt light bulb is power or light output. A 60-watt light bulb emits or puts out more light than a 40-watt light bulb. Light output or power is measured over a period of time in watts. Light bulbs with a higher wattage produce more light; hence, a 60-watt bulb is brighter than a 40-watt bulb.
Light bulbs are made of a filament known as tungsten. As tungsten wire is heated with electrical energy, it gets hot, begins to glow and gives off light. According to How Stuff Works, the tungsten filament within 60-watt incandescent bulbs is 6.5 feet or 2 meters long, only one-hundredth of an inch thick and is wrapped tightly in the form of a double coil. The longer the tungsten filament, the brighter the light emission and the higher the wattage. Since 60-watt light bulbs have a higher wattage than 40-watt bulbs, they also have a longer tungsten filament.
Over the years, newer light bulbs, such as fluorescent, LED and energy-saver light bulbs, have begun to replace Thomas Edison’s incandescent light bulb. According to USA Today, as of Jan. 1, 2014, 60-watt and 40-watt light bulbs cannot be made or imported into the United States. Light bulb companies now offer other forms of light bulbs that emit as much light as the 40- and 60-watt bulb, but require far less energy.