Ray Optics

JEE Main level, numerical answer, medium

138 of 295

Question 138 of 295

Light from a point source in air falls on a spherical glass surface (refractive index, μ=1.5\mu=1.5 and radius of curvature =50 cm=50 \mathrm{~cm}). The image is formed at a distance of 200 cm from the glass surface inside the glass. The magnitude of distance of the light source from the glass surface is ____ m.

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Answer: 4


μ2v−μ1u=μ2−μ1R1.5200−1−x=1.5−150\begin{aligned} & \frac{\mu_2}{\mathrm{v}}-\frac{\mu_1}{\mathrm{u}}=\frac{\mu_2-\mu_1}{\mathrm{R}} \\ & \frac{1.5}{200}-\frac{1}{-\mathrm{x}}=\frac{1.5-1}{50}\end{aligned}
1x=1100−3400x=400 cmx=4m\begin{aligned} & \frac{1}{x}=\frac{1}{100}-\frac{3}{400} \\ & x=400 \mathrm{~cm} \\ & x=4 m\end{aligned}

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