Wave-Particle Duality Just 3 years after Einstein won his Nobel Prize for the photoelectric effect, Louis-Victor de Broglie made a very bold proposal in his doctoral thesis. Light was considered a wave, but in the photoelectric effect it behaves like a particle. What if we took a particle and showed that it can behave like a wave? De Broglie's proposal initially seems strange, but ever since Max Planck solved Black Body Radiation in 1900, strange theories no longer astounded the scientific community. And curiously, de Broglie was right. He not only proved it theoretically but was also able to test his theory with experimental data... In other words, he was able to see particles behaving like waves. After much study, de Broglie arrived at the following mathematical result: Lambda=h/mv Where corresponds to the wavelength... When we have a wave, it is the distance between one peak and another, but this lambda in this formula does not refer to a wave, but to a particle. And this is one of the interesting points of this equation, because it tells you: If this particle were a wave, it would have this wavelength found in this formula. In addition to lambda, we have h, which is Planck's constant (remember that, whenever this h appears, the equation in question is from Quantum Physics), m is the mass of the particle and v is the speed at which it is traveling. Note that mass is a characteristic of particles. So this formula makes a correlation between waves and particles. The idea of ​​wave-particle duality is very simple and you certainly already understand it... It is a wave behaving like a particle and a particle behaving like a wave. However, we need to interpret De Broglie's equation to understand how this phenomenon works. When a particle collides with a barrier, its behavior resembles a billiard ball that bounces and bounces back. Waves, however, are able to get around obstacles using diffraction. This is why a person can get a Wi-Fi signal, even if there is a wall between them and the modem, since Wi-Fi is a type of wave. But there is a detail that we subtly discussed in the experiment on diffraction in class, which gives waves this special characteristic. We saw diffraction happening with a red beam of light, but we needed to use a strand of hair, because wave-like behavior only happens when the barrier has dimensions close to the wavelength. Now pay close attention: Diffraction can define something as a wave. If something undergoes diffraction, that thing is a wave. However, this phenomenon may not happen easily due to the issue of the size of the barrier and the wavelength. When the wavelength is much smaller than the size of the barrier, the wave presents characteristics very similar to particles. It bounces and bounces. Louis De Broglie thought: What if particles, the electron for example... were a wave that never encountered a suitable barrier to exhibit its diffraction behavior? We would think that it is a particle, but perhaps it is not. The de Broglie equation states that all particles have a wavelength, which in this video I will call the “imaginary wavelength,” and through the equation, we can calculate its value. The key point is the relationship between this imaginary wavelength and the mass of the particle. The greater the mass of something, the shorter its wavelength and the lower the barrier that must be for the particle to behave like a wave. The de Broglie equation is more than a simple definition of the wave-particle duality; it represents a boundary between the quantum world and the classical world, the world we are used to. It tells us that strange or quantum behaviors, such as particles behaving like waves and waves behaving like particles, are not something that happens in the macroscopic world, in our everyday lives. Even though we are made of particles, as our atoms interact to form the entire structure that makes up our bodies, in practice we become objects that are too large for there to be any kind of barrier that we can cross through diffraction, that is, we are too large for quantum phenomena, but this does not stop us from creating technologies that can take advantage of these quantum properties. The wave-particle duality brings us a new vision of the world. We could say that all the things we call particles are just waves incapable of demonstrating such characteristics.