A simple explanation of the concept of quantum physics

Have you ever imagined a world that is very small, much smaller than an atom? In this world, the rules we know every day no longer apply. Particles can be in many places at once, influence each other even though they are far away, and can even disappear and reappear in another place. This is the world studied in quantum physics.

Quantum physics, also known as quantum mechanics, is the branch of physics that describes the behavior of matter and energy at the atomic and subatomic levels. It is a fundamental theory that provides a framework for understanding the properties and interactions of particles such as electrons, protons, and photons.

1. Electromagnetic Waves

Initially, physics recognized light as waves like waves in the ocean, ropes that we move up and down (oscillation), and sound. Unlike ocean waves that need water to propagate, light does not need a medium to propagate, it is proven that sunlight can reach the earth even though there is nothing in space. This is because light is an electromagnetic wave. Well, these electromagnetic waves are not just light that we can see, there are ultraviolet, infrared, radio, x-rays, microwaves, and so on, what distinguishes them all is their wavelength. The wavelength will be inversely proportional to the wave frequency. Wavelength is also inversely proportional to the energy of the wave.

Based on the observation results, there are objects that can produce light (lamps, fire, sun) and there are objects that do not produce light (cupboards, beds, tables). Objects that do not produce light can be seen because they reflect light to our eyes. Therefore, when it is dark, we have difficulty seeing these objects.

2. Black body radiation

Even though there are objects that do not produce light, it turns out that actually all objects in the universe produce electromagnetic waves. It's just that the waves produced are not at wavelengths that we can see (visible light). That is why by using special cameras such as infrared cameras we can see these objects. This is what is known as black body radiation. Every object is a black body, only the blackness is different. A perfectly white object is a black object with a blackish level of 0, a perfectly black object is a black object with a blackish level of 1.

The electromagnetic waves produced by a black body are not just 1 wave, but consist of many waves, but there will be 1 wave that is most dominant. The dominant wave depends on the temperature of the object. For example, iron will produce a dominant infrared wave, but when we heat the iron will ignite, indicating that the dominant wave is now visible light. Even so, iron still produces infrared waves. This is what is known as Wien's shift law.

3. UV Catastrophe and Quanta

Physics before quantum physics or what is known as classical physics explained that the energy of waves is inversely proportional to their wavelength. Thus, the dominant wave of black body radiation should be the wave with the smallest length (Rayleigh-Jeans Law). However, it turns out that experimental results state different things, it turns out that in black body radiation, small wavelengths are not dominant. This event is known as UV Catastrophe. The word catastrophe or disaster does not mean there is a real disaster. However, this is a disaster for the world of physics because it turns out that black body radiation cannot be explained by classical physics theory. This caused the world of physics to be in turmoil.

Until finally in 1900, a physicist named Max Planck proposed a new model by modifying it that could match calculation results with observations. The model proposed by Planck is that the energy radiated by a black body is not continuous as in the Rayleigh-Jeans law, but rather like a discrete energy package. The energy package is known as a quanta.

4. Photoelectric and Photon Effects

In 1905, Albert Einstein tested a model initiated by Planck with experimental results observed by Heinrich Hertz in 1887.

In this experiment, when a material is shot with light, electrons will be released from the material, but not as suddenly as when light is shot, the electrons will just be released. There is a minimum energy required for electrons to escape. Using a model initiated by Planck, Einstein stated that the light shot must be at a certain energy, namely the minimum energy of "1 bottle". If the energy is still "1/2 bottle" then the electrons cannot escape.

Electrons that escape also have energy, the amount of which is the difference between the energy of light and the minimum energy of "1 bottle". The magnitude of this energy difference is as if electrons were hit by a small object (particle). These particles are known as photons. This experiment also caused a stir in the world of physics because light, known as waves, apparently has the same properties as particles. 

The results of this hypothesis strengthen Planck's research, in this experiment introducing light dualism or wave-particle dualism.

5. Development of Quantum Physics

Starting from Planck's idea of energy packets, quantum physics developed. The word "Quantum" itself is taken from the word "Kuanta" which is an energy package. The gates to new knowledge are opening and physicists are vying to enter and study quantum physics. Niels Bohr developed the hydrogen atom model, Erwin Schrödinger developed wave mechanics, Max Born introduced a probabilistic interpretation of Schrödinger wave mechanics. Quantum physics finally continues to develop and is starting to be accepted by the wider community.

Finally, a small idea is very, very likely to develop into something big. It's called an idea, it's acceptable or not. Whether an idea is accepted or not triggers many people to prove the idea. In the midst of proving an idea, there will be something new to be learned, a new lesson, new knowledge that may enlighten many people. Therefore, never stop initiating something. Say your ideas.

Thank You.