The 10% of total volume of the barometer liquid (mercury) contains impurities having an average density `5 g cm^(-3)`. When this faulty barometer is used to measure the atmospheric pressure it reads 80 cm of the liquid column. Determine the correct atmospheric pressure.

Explanation

(i) Volume of impurity =0.1 V
Volume of `H_("mercury")=0.9 V`
Density of the liquid in barometer `=("total mass")/("total volume")`
i.e., `d_(1)=(d_(Hg)xx0.9V + d_("impurity")xx 0.1 V)/(V)`
Now the pressure recorded by a standard barometer
`P_(1)=h_(Hg) d_(y) g`
Pressure recorded by faulty barometer
`P_(2)=h_(2)xx dl xx g`
Equate (1) and (2) and determine value at `h_(Hg)`.
(ii) 75 cm