Final answer:
Quantum mechanics is the branch of physics that deals with objects at the atomic and subatomic level. It can be applied to macroscopic objects, but the quantum effects are usually negligible at this scale.
Step-by-step explanation:
Quantum mechanics is the branch of physics that deals with objects at the atomic and subatomic level. While classical mechanics is used to describe the motion of objects at the macroscopic level, quantum mechanics is necessary to accurately describe the behavior of tiny particles like electrons. However, the properties of matter that are described by waves become insignificant at the macroscopic level, so for large systems of matter, the quantum description closely approaches the classical description. This means that quantum physics can be applied to macroscopic objects, but it implies that the quantum effects are usually negligible at this scale.