Quantum Theory

What is Quantum Theory?

Quantum theory also known as quantum physics or quantum mechanics is the foundational basis for present-day material science. The theory basically explains the nature and behaviour of matter and energy on the atomic level. 

Generally, classical physics is often used to explain the occurrences at a macroscopic level. However, quantum theory takes things further and explains the phenomena that occur at the subatomic level. Quantum theory along with general relativity are broad and important fields of Physics which offers a new way of looking at the world. 

Development of Quantum Theory

In the early 1900s, a German physicist named Max Planck stated his quantum hypothesis where he explained that radiation from a sparkling body changed its shades from red to orange to blue when the temperature was increased. This phenomenon was also known as black body radiation.

During his experiments, he found out that energy existed in singular units just like matter instead of consistent electromagnetic wave. With this assumption, it was made clear that energy was quantifiable. The discovery of these units was the primary supposition of quantum hypothesis.

  • Later, Planck composed a numerical condition including a figure to express the individual units of energy. He termed it as quanta. With this, he was further able to solidify his assumption about the findings. Planck won the Nobel Prize in Physics for his hypothesis in 1918, however, advancements by different researchers over a thirty-year time-span all added to the cutting edge comprehension of quantum hypothesis.
  • In 1905, Albert Einstein also took the theory further by stating that radiation apart from energy is quantized in a similar way. He also used the hypothesis to explain the photoelectric effect.
  • Louis de Broglie a French physicist in the year 1924 also suggested that there is no major contrast in the behaviour of matter and energy; In subatomic level, both can act either as waves or particles. This hypothesis is known as the principle of wave-particle duality.
  • Similarly, in the year 1926, an Austrian physicist named Erwin Schrödinger also came up with the partial differential equation for the wave functions of particles. His equation also describes the time evolution of a quantum state.
  • Further, as the years progressed, in 1927, Werner Heisenberg suggested that exact, concurrent estimation of two corresponding qualities, for example, the position and force of a subatomic molecule – is unthinkable. This led to the development of the Heisenberg uncertainty principle.

Quantum Theory’s Influence and Applications

After the establishment of the theory in the previous century, many researchers have worked and developed a new iteration of the quantum hypothesis. Some of the popular ones include the Niel Bohr’s Copenhagen interpretation and the many-worlds or multi-verse theory. Over a span of thirty years or more, there have been different interpretations of the theory as well.

In any case, today the principles of quantum theory are being applied in many fields. Quantum mechanics as such in used to explain the different features of the universe as well as reveal the individual behaviours of subatomic particles such as protons, electrons, neutrons, photons, and others. 

Apart from Physics, quantum mechanics is also used in Chemistry and its application is known as quantum chemistry. Quantum mechanics offers quantitative insight into chemical bonding processes and most of the calculations performed in modern computational chemistry are based on quantum mechanics.

More significantly, most of modern technology is based on the quantum theory where quantum effects are significant.

Some of the other applications of the quantum theory are found in

  • Quantum optics
  • Quantum computing
  • Light-emitting diodes
  • Superconducting magnets
  • Optical amplifier and lasers
  • Transistors
  • Semiconductors
  • Magnetic resonance imaging
  • Electron microscopy and more.


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