A glass tube `80 cm` long and open ends is half immersed in mercury. Then the top of the
Channel: Doubtnut
Date: 02/11/2021

A glass tube `80 cm` long and open ends is half immersed in mercury. Then the top of the tube is closed and it is taken out of the mercury. A column of murcury `20 cm` long then remains in the tube. The atmospheric (in cm of Hg) is   (assume  temperature to be constant )