In terms of Bohr radius $a_o$ the radius of 2nd Bohr orbit of Hydrogen is :
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → $4 a_o$
The radius of the n-th Bohr orbit for the hydrogen atom is -
$r_n=a_0.n^2$
where,
$r_n$ = n-th Bohr obit radius
n = Principle quantum number
$r_1=a_0.(2)^2=4a_0$