Energy is all around us. Energy can be classified as potential or kinetic. Potential energy is stored energy. Kinetic energy is moving energy. There are many types of potential and kinetic energies. Light is a type of kinetic energy because light energy is always moving.
Light energy is a small part of a broader category called electromagnetic energy. Electromagnetic energy is a combination of electrical and magnetic waves. Electromagnetic energy includes the entire electromagnetic spectrum from radio waves to gamma rays.
Humans can only see a small portion of the electromagnetic spectrum called visible light. Visible light is made up of all of the colors in the rainbow. The wavelength of light determines color. Violet has the shortest wavelength, and red has the longest wavelength in the visible light spectrum.
Across the electromagnetic spectrum, wavelength determines energy. The shorter the wavelength, the more energy a wave has. For example, gamma rays have the shortest wavelengths, and they have the most energy. Radio waves have the longest wavelengths and the least energy.
Waves with a lot of energy are harmful to humans and other animals. Gamma rays, x-rays, and ultraviolet rays can damage the cells of the body and cause immediate trauma or lead to cancers. Conversely, low energy waves such as radio waves are not usually dangerous for humans or animals.
The Sun releases most of the electromagnetic energy on Earth, but lightbulbs and fires also emit electromagnetic radiation. However, lightbulbs and fires release much less energy than the Sun because they aren’t as hot. As a result, lightbulbs do not release gamma rays or x rays, but they do release ultraviolet rays, visible light waves, and radio waves. One of the reasons lightbulbs are inefficient is they release extra energy as heat and electromagnetic waves we cannot see.
Light, or electromagnetic, energy is the only energy we can see. It is also the only energy that can travel through space. All other types of energy require atoms or molecules.
Light energy from the Sun is released through nuclear fusion when two hydrogen atoms combine to form a helium ion. Light energy travels outward from the Sun at an incredible 300,000 kilometers per second! Light is the fastest thing in the universe.
Light energy affects almost every part of nature. Light energy heats the Earth unevenly. The equator gets the most direct sunlight, so it is warmer than the north and south poles. Dark areas of Earth absorb more sunlight than light areas, so they are warmer too. This uneven heating drives wind and ocean currents.
Light energy is also a part of the water cycle. Sunlight heats liquid water molecules until they become water vapor. This process is called evaporation.
Light energy provides plants with energy for photosynthesis. Without plants, animals on Earth would have nothing to eat. Plants also produce the oxygen we breathe as a byproduct of photosynthesis.
Humans have also learned to convert light energy into electrical energy through solar panels. Light energy is a clean, renewable energy because it doesn’t release any pollution, and it is continually provided by the Sun. Solar panels are being improved to be more efficient and cost-effective. Special batteries have also been invented, so light energy can be stored and used at night or when it is cloudy.
Without light energy, we could not live on Earth. Other types of electromagnetic energy do important jobs on Earth as well. For example, flowers have ultraviolet patterns on their petals that show bees where to land to collect nectar. These patterns are invisible to humans because we cannot see within the ultraviolet part of the electromagnetic spectrum, but bees can. As we learn more about the world around us, we learn more about the ways light energy, and all electromagnetic energy, affects life on Earth.