Question

where particles are localized?in short
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Answer 1

Answer:

may be found within a region (e.g. a ball) whose linear size is smaller (or much smaller)

hope it helps ✌️

Answer 2

Answer:

localized state of a particle or a field means the same thing as in semi-colloquial context: it means that most of the energy density (for the case of a field) or most of the probability (particle, quantum mechanics) may be found within a region (e.g. a ball) .