Using Bohr's postulates of the atomic model, derive the expression for radius of nth electron orbit. Hence obtain the expression for Bohr's radius.

Centripetal force is provided by the electrostatic force of attraction.
mv²r = e²/4πε₀r²
From Bohr's second postulate,
Lₙ = mvn rₙ = nh/2π
Eliminating vₙ from above equations.
rₙ = n²h²ε₀π/me²
Bohr's radius is the radius of the innermost orbit. Hence, n=1
r₁ = h²ε₀π/me²