Correct Answer: 720 N/m^{2}
Explaination::
Given : Radius of bubble =0.2 mm =\(2\times 10^{-4} m\) , surface tension of water = 0.072 N/m = \(720\times 10^{-4} N/m\)
We know that, excess pressure inside a air bubble in a liquid is given by
Where, t = surface tension of liquid r = radius of bubble
Thus,
The gauge pressure = \(2\times 720\times 10^{-4}\over 2\times 10^{-4}\) = 720 N/m^{2}