According to the concept of Bohr's orbit, the angular momentum of electrons in circular orbits is quantized.
i.e., Orbital angular momentum, L = m v r = (n h) / [2 (pi)], where n = 1,2,3 .............
i.e. the values of L are finite
So, uncertainty in determining L = Delta L = 0
So, uncertainty in determining (theta) = Delta (theta) = Infinite

Thus, the concept of Bohr orbit violets the uncertainty principle i.e. the uncertainty relation Delta L x Delta (theta) is greater than or equal to h.

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By :-   Dr. A. W. Pangantiwar