 Solution

ID: past-exam-of-the-mphil-in-micro-and-nanotechnology-enterprise-course-of-the-university-of-cambridge/2020/paper-1/section-b/10/i/a/solution

A soap film has two air-water interfaces. The Young–Laplace equation therefore gives

Δ p = \frac{4 γ}{r} = \frac{4 ( 0.025 )}{0.10} = 1.00 Pa .

The radius is half the specified diameter; using the single-interface droplet expression would miss a factor of two.

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