What is the ratio of radii of `3^"rd"` and `2^"nd"` orbit of hydrogen atom ?

Explanation

To find the ratio of the radii of the 3rd and 2nd orbits of a hydrogen atom, we can use Bohr's model of the atom, which states that the radius of an orbit is directly proportional to the square of the principal quantum number (n).

### Step-by-Step Solution:

1. **Understand the relationship**: According to Bohr's model, the radius (r) of an orbit is given by the formula:
\[ r \propto n^2 \]
...