In a faulty barometer some air occupying the space over mercury column. How can the air pressure be correctly determined with this faulty barometer?

In a faulty barometer some air occupying the space over mercury column

1.	In a faulty barometer some air occupying the space over mercury column. How can the air pressure be correctly determined with this faulty barometer?
Answer» SOLUTION :LET the length of mercury column =`h_1`, and that of air column over mercury `=l_1` now the barometer tube is raised a little still keeping the OPEN END dipped into mercury. Let in this case,the length of mercury column=`h_2`, and that of air column over mercury `=l_2`. If the true reading of the air pressure is H, and the area of cross section of the tube is a, then from Boyle.s LAW `(H-h_1)l_1a=(H-h_2)l_2aor,H=(h_1l_1-h_2l_2)/(l_1-l_2)` Hence, measuring `h_1,h_2,l_1,l_2` the correct atmospheric pressure can be find out.