Hola! I'm Alexa Guido, a young and curious woman passionate about science. Join me on an exciting journey to explore the wonders of the universe through the lens of physics.
Did you know that Albert Einstein did not win the Nobel Prize in 1921 due to the Theory of Relativity? Actually, he was awarded because he explained the photoelectric effect [1], beginning with a new chapter in Physics History.
The photon, the particle that is everywhere and made the quantum revolution start, was the main character of a dramatic rivalry between physicists in the XIX Century, and challenged everyone with a contradictory question “Does light behave as a particle or as a wave?” I am happy to introduce you to photons.
In a nutshell, photons are light, but what does that mean? We have to start this journey with Christiaan Huygens in 1690, who described light was made up of waves that move through the ether [2]. Then in 1704, Isaac Newton rejected that theory and offered a new one “Light acts like a bouncing ball”, he said.
Imagine that you are in a completely dark room, and you put a lantern forcing the light to travel through a small hole, now you look to the other side you will see that it spreads out just like waves in water. However, Newton’s corpuscular model couldn’t explain this behavior, and Huygens’ wave model could.
This inquiry traveled through a lot of physicists, but one came up with a different idea. In 1900, Max Planck stated that light waves travel as separate packets of energy called quanta or photos, becoming the father of an incredible unification of Corpuscular, Wave, and Electromagnetic theories. Finally, in 1905, Albert Einstein built on Planck’s concept of energy packets and finally settled the corpuscule-versus-wave debate—by declaring it a tie.
The concept of photons is continuously changing. Now the photon is known as a “gauge boson”, by means of being a force-carry particle that enables matter particles to interact via the fundamental forces. Even the photon is now considered a particle, a wave, and an excitation in a quantum field.
Photons are the smallest particles of electromagnetic energy, they can travel at the speed of light because they neither have mass, nor charge. Photons represent the entire spectrum of electromagnetic radiation and have a whole spin.
They travel in a wave-like fashion, in which the electric and magnetic field oscillates in intensity, regularly swinging back and forth between high and low energy levels, being a transverse wave. Likewise, the energy in the photons determines the type of electromagnetic radiation the photons transmit. This indicates that low-energy photons carry radio waves. Radio waves are called long-wavelength because the bottoms and crests of the waves are relatively far apart. High-energy photons carry gamma waves. Gamma waves are called short-wavelength because the bottoms and crests of their waves are very close together.
Have you ever wondered the reason why the sun heats us? Photons can be absorbed by matter. When this happens, their light is transformed into heat, warming the matter, and warming us. As we said in the beginning, photons are everywhere, and in any action you do, even photons appear in the annihilation of a particle with its antiparticle, which is incredible! We can talk about photons for years!
[1] This is the way a sheet of metal emits electrons when hit with light.
[2] From the Cambridge Dictionary “the sky or the air, especially considered as being full of radio waves”
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