Bohr's theory of the atom was proposed in the early 20th century and was based on the idea that electrons move in fixed orbits around the nucleus. According to this theory, the position and momentum of an electron in an atom can be determined with absolute precision at any given moment, which seems to contradict Heisenberg's uncertainty principle.
Heisenberg's uncertainty principle states that it is impossible to determine the exact position and momentum of a particle simultaneously. This means that the more accurately we measure the position of a particle, the less accurately we can measure its momentum, and vice versa. This principle applies to all particles, including electrons in an atom.
The failure of Bohr's theory to explain the Heisenberg uncertainty principle is due to its assumption that electrons move in well-defined orbits around the nucleus. In reality, electrons do not follow a fixed path, but rather exist as a probability distribution around the nucleus. This means that the more precisely we measure the position of an electron, the less certain we become about its momentum, as the act of measurement disturbs the electron's position.
Thus, Bohr's theory fails to explain the Heisenberg uncertainty principle because it assumes that the position and momentum of an electron in an atom can be determined with absolute precision, whereas the uncertainty principle shows that there is a fundamental limit to how accurately both of these quantities can be known at the same time.