Question

An air bubble in a glass sphere $(\mu = 1.5)$ is situated at a distance $3\, cm$ from a convex surface of diameter $10\, cm$. At what distance from the surface will the bubble appear?

• A. $2.5 \,cm$
• B. $-2.5 \,cm$
• C. $5 \,cm$
• D. $-5 \,cm$

Answer 1

Answer: (B)

$-2.5 \,cm$

Answer 2

Since refraction occurs from denser to rarer medium, Therefore, $-\frac{\mu_{2}}{u} +\frac{\mu_{1}}{v} = \frac{\mu_{1}-\mu_{2}}{R}$ $- \frac{3}{2\left(-3\right)}+\frac{1}{v} = \frac{1-\frac{3}{2}}{-5} = \frac{1}{10}$ or $\frac{1}{v}=\frac{1}{10} -\frac{1}{2} = -\frac{4}{10}$ $\Rightarrow v = -2.5 \,cm$