Question

The radii of curvature of the faces of a double convex lens are 10 cm and 15 cm. If focal length of the lens is 12 cm, find the refractive index of the material of the lens.

Answer 1

As We know the radii of the curvature of the faces of a double convex lens are 10cm and 15cm.

• Focal length (f) of the lens is 12 cm.

➣Now By using Formula, we're able to find the Refractive index (μ) of the lens.

→ 1/f = (μ – 1) (1/R₁ – 1/R₂)

→ 1/12 = (μ – 1)(1/10–1/15)

→ 1/12 = (μ –1)(3–2/30)

→ 1/12 = (μ–1)(1/30)

→ 1/12 = (μ–1)/30

→ 30/12 = (μ–1)

→ 5/2 = (μ–1)

→ 5/2 + 1 = μ

→ μ = 7/2

→ μ = 3.5

Hence,

The Refractive index (μ) of the lens will be 3.5