Write the Bohr's frequency condition.

Explanation

To write Bohr's frequency condition, we will follow these steps:

### Step 1: Understand the Concept of Energy Levels
Bohr's model of the atom describes electrons orbiting the nucleus in specific energy levels or shells. When an electron transitions between these energy levels, it either absorbs or emits energy.

### Step 2: Identify the Energy Transition
When an electron moves from a higher energy level (n=2, n=3, etc.) to a lower energy level (n=1, n=2, etc.), energy is released. Conversely, when it moves from a lower energy level to a higher energy level, energy is absorbed.

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