Find the ratio of velocities of electron in `2^"nd"` and `4^"th"` orbit of hydrogen atom.

Explanation

To find the ratio of velocities of the electron in the 2nd and 4th orbit of a hydrogen atom, we can follow these steps:

### Step 1: Understand the formula for velocity
The velocity of an electron in a hydrogen atom is given by the formula:
\[ V_n = \frac{c}{137} \cdot \frac{Z}{n} \]
where:
- \( V_n \) is the velocity of the electron in the nth orbit,
- \( c \) is the speed of light,
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