A simple mercury barometer is used to measure atmospheric pressure at a location near sea level.
a. (i) Describe, in words only, the essential construction and working of the instrument.
b. (ii) State the mathematical relation that links the atmospheric pressure P0, the density ρHg of mercury and the vertical height h of the mercury column.
c. (iii) Explain why the barometric height is nearly 76cm at sea level even though the pressure on the free surface of the mercury reservoir is the same as that on the top of the mercury column which is almost a vacuum.
d. (iv) Mention any two assumptions made while establishing the relation in part (ii).