Question

The vertical height of mercury which a simple barometer can support at sea level is

• A. $76cm$
• B. more than $76cm$
• C. less than $76cm$
• D. none of these

Answer 1

The correct option is C less than $76cm$

Answer is C.

The mercury level in the tube of the barometer falls until it is about $76cm\left(760mm\right)$ vertically above the mercury level. It is the atmospheric pressure acting on the surface of the mercury in the trough that supports the vertical mercury column.
The atmospheric pressure is therefore specified by so many millimetres of mercury. For example, the atmospheric pressure is $760mm$ Hg at sea level.
Hence, The vertical height of mercury which a simple barometer can support at sea level is less than 76 cm.