Understanding Parity in Quantum Mechanics

[Brewer]

As part of an exam paper I've been using to revise with, I came across a question that simply says "What is parity?"

Well I know vaguely what it is. Its to do with whether a wave is odd or even right?

For example for cos and sin
odd parity occurs because sin(-x) = -sin(x)
and cos(-x) = cos(x) means that the function has even parity.

But I what I don't know is how I would word the answer to the question "What is parity?". How would you do it?

It only occurs (in the quantum-mechanical sense (very basic intro level)) if the wave function is centralised about the origin of the scale, right?

Any hints as how to go about answering this would be appreciated.

 

[berkeman]

Parity has multiple meanings. Check out the list at wikipedia.org:

http://en.wikipedia.org/wiki/Parity

 

[m2003]

Parity is a fundamental concept in quantum mechanics that describes the symmetry of a physical system under spatial inversion. In simple terms, it refers to whether a system remains unchanged when its coordinates are inverted or reflected. This concept is important in understanding the behavior of particles and their interactions at the quantum level.

In more technical terms, parity is a quantum number that represents the intrinsic symmetry of a particle or a system. It can have two possible values, either +1 or -1, which correspond to even and odd symmetries, respectively. This quantum number is conserved in many physical processes, meaning it remains constant throughout the system's evolution.

In terms of wave functions, parity is determined by the behavior of the wave function under spatial inversion. An even parity wave function remains unchanged when its coordinates are inverted, while an odd parity wave function changes sign. This can be observed in the example given in the question, where the cos function has even parity and the sin function has odd parity.

Parity plays a crucial role in understanding the behavior of particles and their interactions, particularly in nuclear and particle physics. It helps classify particles and their states, and also plays a role in determining the selection rules for certain physical processes.

In summary, parity is a fundamental concept in quantum mechanics that describes the symmetry of a system under spatial inversion. It is represented by a quantum number and is conserved in many physical processes. Understanding parity is essential for understanding the behavior of particles and their interactions at the quantum level.