Published by:
CGP EDU Academic Team
Published on: September 12, 2026
A soap bubble assumes a spherical surface. Which of the following statement is wrong
Text Solution
Verified by ExpertsThe correct answer is:
C
Step 1: Understand the pressure relationships in a soap bubble. A soap bubble does enclose air inside it, and the pressure inside a soap bubble (the pressure of the enclosed air, denoted as P_in) is actually greater than the atmospheric pressure (P_atm). This is due to the surface tension of the soap film, which creates a pressure difference between the inside and outside of the bubble.
Step 2: According to the Young-Laplace equation, the pressure difference across the surface of a soap bubble is given by:
$$ P_{in} - P_{out} = \frac{4\gamma}{R} $$
where \( \gamma \) is the surface tension of the soap film and R is the radius of the bubble. Since \( P_{out} \) (atmospheric pressure) is less than \( P_{in} \), it confirms that the inside pressure is indeed greater than atmospheric pressure.
Step 3: This makes Option C incorrect because it states that the pressure of the air inside the bubble is less than atmospheric pressure, which is not true.
Conclusion: Therefore, Option C is the wrong statement.
Step 2: According to the Young-Laplace equation, the pressure difference across the surface of a soap bubble is given by:
$$ P_{in} - P_{out} = \frac{4\gamma}{R} $$
where \( \gamma \) is the surface tension of the soap film and R is the radius of the bubble. Since \( P_{out} \) (atmospheric pressure) is less than \( P_{in} \), it confirms that the inside pressure is indeed greater than atmospheric pressure.
Step 3: This makes Option C incorrect because it states that the pressure of the air inside the bubble is less than atmospheric pressure, which is not true.
Conclusion: Therefore, Option C is the wrong statement.
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