Invariance under a spatial reflection. A one-dimensional Quantum Hamiltonian invariant under admits energy eigenfunctions of definite even or odd midpoint parity. Even and odd functions are orthogonal on a reflection-symmetric interval.
A plane through which reflection leaves an object unchanged. In a molecular skeleton, sites exchanged by a symmetry preserving all substituent identities can be chemically equivalent in an achiral NMR spectroscopy experiment.
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Reflection symmetry, also known as mirror symmetry or bilateral symmetry, is a type of symmetry where one half of an object or shape is a mirror image of the other half. In simpler terms, if you were to draw a line (called the line of symmetry) through the object, the two halves on either side of the line would match perfectly when flipped over that line. Reflection symmetry is commonly found in nature and art.