What is the circumference of the second orbit of hydrogen atom ?

Explanation

Circumference `= 2pi r`
But `r = n^(2) xx 0.529 A^(0) = 2^(2) xx 0.529 A^(0) = 2.116 A^(0)`
Circumference `= 2 xx 3.14 xx 2.116 A^(0) = 13.3 A^(0)`