quantum mechanics
Definition
Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, quantum field theory, quantum technology, and quantum information science.
Quantum mechanics differs from classical physics in many ways, including:
- Quantization: in quantum mechanics, energy, momentum, angular momentum, and other quantities are often restricted to discrete values.
- Wave-particle duality: objects have characteristics of both particles and waves.
- The uncertainty principle: it is impossible to simultaneously know both the position and momentum of a particle with perfect accuracy.
- The superposition principle: a quantum system can exist in multiple states at the same time.
Quantum mechanics has had a profound impact on our understanding of the universe. It has led to the development of new technologies such as lasers, transistors, and nuclear weapons. It has also challenged our understanding of reality and the nature of the universe.
How can the word be used?
Quantum mechanics is the foundation of modern physics.
Different forms of the word
Noun: quantum mechanics (plural: quantum mechanics).
- a physical theory that describes the behaviour of matter and energy at the atomic and subatomic level.
Adjective: quantum.
- relating to quantum mechanics.
Verb: to quantize.
- to describe something in terms of quantum mechanics.
Etymology
The word "quantum mechanics" comes from the Latin word "quantus" (how much) and the Greek word "mechanica" (of mechanics).
The word "quantum mechanics" was first used in English in the early 20th century. It was used to refer to the new branch of physics that was developing at the time to explain the behavior of matter and energy at the atomic and subatomic level.
Question
What is quantum mechanics?
AQA Science Exam Question and Answer
Question:
What is the key principle of quantum mechanics, and how does it challenge our classical understanding of the physical world? Provide a simple example to illustrate this principle.
Answer:
The fundamental principle of quantum mechanics is that particles, such as electrons and photons, can exist in multiple states or locations simultaneously until they are observed or measured. This concept is known as superposition and challenges the classical understanding of a particle having a definite position or state at all times.
For instance, consider the famous thought experiment of Schrödinger's cat. Imagine a cat in a sealed box with a radioactive atom that may or may not decay, releasing poison and killing the cat. According to quantum mechanics, until the box is opened and observed, the cat exists in a superposition of being both alive and dead simultaneously. This bizarre notion illustrates the challenge quantum mechanics poses to our classical intuition, where objects are typically thought to exist in definite states.
This principle becomes more profound in the context of the double-slit experiment. When particles, like electrons or photons, are sent through two slits and observed on a screen, they exhibit interference patterns, as if they were waves. This suggests that these particles exist in multiple states and interfere with themselves, highlighting the inherent uncertainty in their behaviour.