Question

The combination of convex lense and concave lense have power +2 D if the focal length of convex lense is 25cm. Calculate the focal length of concave lense used in this combination

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Answer 1

Answer:

Here's urs answer sis f = -0.5 m

Explanation:

Given:

The combination of the convex lens and concave lens has power +2 D if the focal length of the convex lens is 25cm = 25/100 m = 0.25m

The focal length of convex lens=?

Power of convex lens (P₁)= 1/0.25m = 100/25 = 4

Combine power = P₁ + P₂

⇒ 2 = 4 + P₂

⇒ P₂ = 2-4

⇒ P₂ = 2-4

⇒ P₂ = -2

Now,

P₂ = 1/f₂

⇒ -2 = 1/f

⇒ f₂ = -1/2 m