The question asks for the average atmospheric pressure at sea level. This is a standard value in meteorology and atmospheric science that competitive exam aspirants should be familiar with.
Correct Option: D) 1013.2 mb
The question asks for the correct definition of atmospheric pressure in terms of the column of air considered. Atmospheric pressure is essentially the force exerted by the air above a given point due to gravity, divided by the area over which this force is distributed.
D) Mean sea level to the top of the atmosphere. This option correctly identifies both the starting point (mean sea level, a standard reference for measuring atmospheric pressure) and the extent of the air column (to the top of the atmosphere, encompassing all the air above). The weight of this entire column of air, per unit area, defines the atmospheric pressure at mean sea level.
The question asks to identify the instrument used for measuring atmospheric pressure. We need to recall the functions of the given instruments.
Let's analyze each option:
Based on this analysis, the barometer is the correct instrument for measuring atmospheric pressure.
Correct Option: A) Barometer is specifically designed and used to measure atmospheric pressure.
The question asks for the unit in which atmospheric pressure is expressed. This requires knowledge of common units used for measuring atmospheric pressure.
Considering the context of competitive exams, 'millibar' is a very specific and widely recognized unit for atmospheric pressure, especially in meteorology, which is often covered in general science sections.
D) Millibar (mb) — Millibar is a widely used unit for expressing atmospheric pressure, particularly in meteorology. Standard atmospheric pressure at sea level is approximately \(1013.25 \text{ mb}\).
Atmospheric pressure is caused by the weight of the air column above a given point. To understand how it changes with altitude, we need to consider the density and amount of air present at different heights.
A) Decreases with altitude. As explained, with increasing altitude, the column of air above a point becomes shorter and less dense, resulting in a lower weight of air and thus lower atmospheric pressure.
The question asks about the approximate rate at which atmospheric pressure decreases with increasing altitude in the lower atmosphere. This is a standard concept in meteorology and atmospheric science. We need to recall the typical pressure lapse rate near the Earth's surface.
Correct Option: C) 1 mb per 10 m increase