[NEET 2019] In hydrogen atom, the de Broglie wavelength of an electron in the second Bohr orbit is (Bohr radius a₀ = 52.9 pm)

For nth orbit: 2πrₙ = nλ (de Broglie condition). r₂ = 0.529 × 4/1 = 2.116 Å = 211.6 pm. λ = 2πr₂/n = 2π × 211.6/2 = 211.6π pm.