At higher altitudes the height of mercury column in a barometer will be ____________

Explanation

**Step-by-Step Solution:**

1. **Understanding Barometer Functionality**: A barometer is a device used to measure atmospheric pressure. It consists of a column of mercury, and the height of this mercury column changes with variations in atmospheric pressure.

2. **Effect of Altitude on Atmospheric Pressure**: As we ascend to higher altitudes, the atmospheric pressure decreases. This is because there is less air above us exerting pressure.

3. **Relationship Between Pressure and Mercury Height**: The height of the mercury column in a barometer is directly proportional to the atmospheric pressure. This means that when the atmospheric pressure increases, the height of the mercury column also increases, and when the atmospheric pressure decreases, the height of the mercury column decreases.

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