Calculate the radius of smallest orbit of a hydrogen atom.

Explanation

To calculate the radius of the smallest orbit of a hydrogen atom, we will use the Bohr model of the atom. Here are the steps to derive the radius:

### Step 1: Understand the Bohr Model
According to the Bohr model, electrons revolve around the nucleus in circular orbits due to the electrostatic force of attraction between the positively charged nucleus (proton) and the negatively charged electron.

### Step 2: Set Up the Forces
The centripetal force required for the electron to move in a circular orbit is provided by the electrostatic force between the proton and the electron. This can be expressed as:
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