Question

The ratio of radius of $2^{nd}$ and $3^{rd}$ Bohr's orbit is:

• A. 3 : 2
• B. 9 : 4
• C. 2 : 3
• D. 4 : 9

Answer 1

The correct option is D 4 : 9

We know that the radius of an orbit in a hydrogen atom is directly proportional to $n^2$.

Therefore, the ratio of the radius of $2^{nd}$ orbit to the radius of $3^{rd}$ orbit $=\frac{2^2}{3^2}=\frac{4}{9}$.

Hence, option D is correct.