Question

The excess pressure inside a soap bubble is three times than excess pressure inside a second soap bubble, then the ratio of their surface area is

• A. (a) 9 : 1
• A. (b) 1 : 3
• A. (c) 1 : 9
• A. (d) 3 : 1

Answer 1

(c) Pressure

Or

$\therefore \frac { \mathrm { P } _ { 1 } } { \mathrm { P } _ { 2 } } = \frac { \mathrm { r } _ { 2 } } { \mathrm { r } _ { 1 } } = \frac { 3 } { 1 }$ …… (i)

Or

Also $\frac { \mathrm { A } _ { 1 } } { \mathrm {~A} _ { 2 } } = \frac { 4 \pi \mathrm { r } _ { 1 } ^ { 2 } } { 4 \pi \mathrm { r } _ { 2 } ^ { 2 } } = \left( \frac { \mathrm { r } _ { 1 } } { \mathrm { r } _ { 2 } } \right) ^ { 2 }$

(Using (i))

$= \frac { 1 } { 9 }$