The radii of curvature for a thin convex lens are 10 cm and 15 cm respectively. The focal length of the lens is 12 cm. The refractive index of the lens material is [2025]

Question

The radii of curvature for a thin convex lens are 10 cm and 15 cm respectively. The focal length of the lens is 12 cm. The refractive index of the lens material is [2025]

Smart Achievers · Accepted Answer

(3)

For bi-convex

$R_{1} = 10 cm, R_{2} = - 15 cm$

$\frac{1}{f} = (μ - 1) (\frac{1}{R_{1}} - \frac{1}{R_{2}})$

$\frac{1}{12} = (μ - 1) (\frac{1}{10} - \frac{1}{- 15}) = (μ - 1) (\frac{1}{6})$

$μ - 1 = \frac{1}{2} \Rightarrow μ = 1.5$

Solution

Q.
The radii of curvature for a thin convex lens are 10 cm and 15 cm respectively. The focal length of the lens is 12 cm. The refractive index of the lens material is [2025]

1 1.2

2 1.4

3 1.5

4 1.8

Ans.
(3)

For bi-convex

$R_{1} = 10 cm, R_{2} = - 15 cm$

$\frac{1}{f} = (μ - 1) (\frac{1}{R_{1}} - \frac{1}{R_{2}})$

$\frac{1}{12} = (μ - 1) (\frac{1}{10} - \frac{1}{- 15}) = (μ - 1) (\frac{1}{6})$

$μ - 1 = \frac{1}{2} \Rightarrow μ = 1.5$

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