# Solve Numerical example. A point object is kept 10 cm away from one of the surfaces of a thick double convex lens of refractive index 1.5 and radii of curvature 10 cm and 8 cm. - Physics

Numerical

Solve Numerical example.

A point object is kept 10 cm away from one of the surfaces of a thick double convex lens of refractive index 1.5 and radii of curvature 10 cm and 8 cm. Central thickness of the lens is 2 cm. Determine location of the final image considering paraxial rays only.

#### Solution

Given that, R1 = 10 cm, R2 = – 8 cm, u = – 10 cm and n = 1.5
From lens maker’s equation,

1/"f"=("n"-1)(1/"R"_1-1/"R"_2)

∴ 1/"f"=(1.5-1)(1/10-1/-8)

= 0.5xx9/40=9/80

∴ f = 80/9 cm

Now,

1/"f"=1/"v"-1/"u"

∴ 1/"v"=1/"f"+1/"u"=9/80+1/-10=1/80

∴ v = 80 cm

The final location of the image will be at 80 cm from the lens.

Concept: Refraction at a Spherical Surface and Lenses
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#### APPEARS IN

Balbharati Physics 11th Standard Maharashtra State Board
Chapter 9 Optics
Exercises | Q 4. (viii) | Page 187