# Two convex lenses of focal length 30 cm and 10 cm each are kept in contact with each other. Find the power of their combination - Science and Technology 1

Numerical

Two convex lenses of focal length 30 cm and 10 cm each are kept in contact with each other. Find the power of their combination.

#### Solution

Given: f1 = 30 cm = 0.30 m, f2 = 10 cm = 0.10 m

To find: Power of combination (P)

Formula: P = 1/"f" = 1/"f"_1 + 1/"f"_2

Calculation: From formula,

P = 1/"f" = 1/0.30 + 1/0.10 = 1/0.30 + 3/0.30

= 4/0.30 = 13.33 D

Power of combination is 13.33 D.

Concept: Combination of Lenses
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