What is quantum mechanics?

Quantum mechanics is a theory of physics that governs the very small world (atoms, electrons, photons, etc.).

It explains phenomena in the microscopic world that cannot be explained by classical mechanics (Newtonian mechanics).

 

Why was it necessary?

In the 19th and early 20th centuries, classical mechanics could not explain these phenomena:

• Black body radiation spectrum

• Photoelectric effect

• Atomic spectrum (line spectrum)

• Stable orbits of electrons

Planck, Einstein, Bohr, Heisenberg, Schrödinger, and others developed theories to explain them.

 

Key Concepts

① Quantization

• Energy is not continuous but divided into discrete 'quantum units'

• Example: Energy levels of electrons

 

② Wave-particle duality

• Electrons and light behave as both particles and waves

• Photons (particles of light) cause interference and diffraction

• Electrons also form interference patterns like waves

 

③ Uncertainty Principle

• Heisenberg Uncertainty Principle:

 

④ Wave function (ψ)

Describe the state of a particle using a wave function

Calculate probability:

 

⑤ Schrödinger Equation

• Determines how the wave function of a particle changes over time

• Representative predictions of quantum mechanics

• Stable orbit of electrons (Bohr model)

• Tunneling phenomenon (quantum tunneling)

• Spin (intrinsic angular momentum)

• Quantum entanglement (the states of two particles are linked)

• Applications in daily life

• Semiconductors, transistors

• Lasers

• MRI

• Quantum cryptography

• Quantum computers

 

One sentence summary

"Quantum mechanics is the theory that particles in the microscopic world behave probabilistically, like waves, and break classical intuition