According to Bohr's postulates, the quantity that shows discrete valu…

The correct answer is Option (2) → Angular momentum

Bohr's second postulate (the quantisation condition) states that an electron can revolve only in those orbits in which its angular momentum is an integral multiple of \( h/2\pi \):

    \( \displaystyle L = mvr = \frac{nh}{2\pi}, \qquad n = 1, 2, 3, \ldots \)

So the quantity that the postulate itself restricts to discrete values is the angular momentum. The discrete radii and energies of the orbits are derived from this condition; they are consequences, not the quantity postulated.

NCERT (2026-27):
Bohr Model of the Hydrogen Atom – “… (ii) Bohr’s second postulate defines these stable orbits. This postulate states that the electron revolves around the nucleus only in those orbits for which the angular momentum is some integral multiple of h/2π where h is the Planck’s constant (= 6.6 × 10⁻³⁴ J s). Thus the angular momentum (L) of the orbiting electron is quantised. That is

    \( \displaystyle L = nh/2\pi \qquad (12.5) \) ”