Atmospheric Pressure is measured by _____.

Barometer

The correct answer is option 4. Barometer.

Atmospheric pressure is the force per unit area exerted by the weight of the atmosphere above a given point. It is a measure of the weight of the air above a specific location and is influenced by factors such as altitude, temperature, and weather conditions.

A barometer is the instrument used to measure atmospheric pressure. There are various types of barometers, but one common design is the mercury barometer. In a mercury barometer, a vertical glass tube is filled with mercury, and then inverted into a container of mercury. The mercury column in the tube adjusts to the height at which the atmospheric pressure balances the weight of the mercury column. The height of the mercury column is directly proportional to the atmospheric pressure. Atmospheric pressure is often measured in units such as millimeters of mercury (mmHg) or hectopascals (hPa).

By measuring the height of the mercury column in the barometer, one can determine the atmospheric pressure at a specific location. This measurement provides important information for weather forecasting, aviation, and other applications where knowledge of atmospheric pressure is crucial.

In summary, a barometer is used to measure atmospheric pressure by determining the height of a column of mercury or other liquid in response to the atmospheric pressure acting on it.