Scuba Diver Bubble: Diameter at Surface?

[pkossak]

A spherical air bubble originating from a scuba diver at a depth of 18 m has a
diameter of 1 cm. What will the bubble's diameter be when it reaches the
surface? (Assume constant temp)
a. 0.7 cm b. 1 cm c. 1.4 cm d. 1.7 cm

I know this problem shouldn't be all that difficult, but I'm not sure how to convert the depth into pressure. I would think they would say whether or not the water was sea water, so I was wondering if there was another way to figure this out other than through using density. Maybe I am over analyzing and that part was simply left out, but I just wanted to be sure. Thanks again help.

 

[mathmike]

yes i believe you are making it harder than it really is.

hydrostatic pressure is defined by

p = density * height of liquid

try this and see if it helps

 

[pkossak]

Thanks for the help. I ended up using p = po + density*g*h and got the answer I was looking for.