Explain why does the mercury level in a barometer go down when atmospheric pressure decreases?

Explanation

To explain why the mercury level in a barometer goes down when atmospheric pressure decreases, we can break down the explanation into a series of logical steps:

### Step-by-Step Solution:

1. **Understanding the Barometer**: A barometer is a device used to measure atmospheric pressure. It typically consists of a glass tube filled with mercury, inverted in a reservoir of mercury.

2. **Role of Atmospheric Pressure**: The atmospheric pressure is the force exerted by the weight of air molecules in the atmosphere. This pressure acts on the surface of the mercury in the reservoir.

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