Have you heard about Planck's constant?
- Alexa Ines Guido
- Jul 16
- 3 min read
Updated: Aug 10
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.
One hundred years ago, Werner Heisenberg retreated to the island of Helgoland, where he built the foundations of the first full formulation of quantum mechanics. But let’s take a step back: who actually started the quantum revolution? And how did physicists begin to understand the concept of quantification?
Back in the early 1900s, scientists were faced with an experimental phenomenon that classical physics simply couldn’t explain: blackbody radiation. This term describes the spectrum of light emitted by any heated object, including us humans! Every object, when heated, emits a type of radiation, yet all attempts to explain or calculate this spectral distribution using classical theories failed miserably.
In particular, a theory developed by Rayleigh and Jeans predicted that the intensity should go to infinity at short wavelengths.
Since the intensity actually drops to zero at short wavelengths, the Rayleigh-Jeans result was called the famous ultraviolet catastrophe. There was no agreement between theory and experiment in the ultraviolet region of the blackbody spectrum.
However, in 1900, the German physicist Max Planck proposed a groundbreaking idea: what if the energy of electromagnetic waves is quantized rather than continuous? This meant that for any given temperature, there’s a maximum intensity of radiation that a blackbody can emit. So instead of a smooth curve as classical physics suggested, the intensity behaves in a more discrete manner. Thus, energy could be gained or lost only in integral multiples of some smallest unit of energy, a quantum (the smallest possible unit of energy).
At the time he proposed his radical hypothesis, Planck could not fully explain why energies should be quantized. Initially seen as a mere mathematical trick, turned out to be right, and was able to explain only one set of experimental data, the blackbody radiation.
If quantization were observed for a large number of different phenomena, then quantization would become a law. As fate would have it, Planck’s hypothesis was indeed accurate, becoming the seed that would eventually sprout into the vast field of modern physics.
Planck's quantization of energy is described by his famous equation:
E=hν
where the proportionality constant h is called Planck’s constant, one of the most accurately known fundamental constants in science
h=6.626070040(81)×10−34J⋅s
Planck’s constant is crucial in the world of quantum mechanics. It sets the scale for quantum effects and acts as the bridge between the energy of a photon and the frequency of its corresponding electromagnetic wave. Interestingly, it wasn’t until 2011 that an experiment at the Large Hadron Collider finally determined the value of the Planck constant with precision!
Without it, quantum theory would be mathematically incoherent! It sets the scale for a multitude of phenomena, from the behavior of electrons in atoms to the properties of the early universe.
For his groundbreaking discovery of energy quanta, Max Planck was awarded the Nobel Prize in Physics in 1918, effectively laying the groundwork for quantum theory. His introduction of the Planck constant revolutionized our understanding of atomic and subatomic processes.
One of the first real applications of Planck’s constant was the Bohr model of the hydrogen atom. The quantization of angular momentum within this model is directly linked to Planck’s constant, helping to explain phenomena like atomic spectra.
So there you have it! Planck's revolutionary ideas not only sparked the quantum revolution but also reshaped our understanding of the universe at its most fundamental level.
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