Question

If the power of lenses A and B are in the ratio 3:1, what would be the ratio of the focal length of A and B?​

Answer 1

Answer:Ratio of powers = 4 : 1

Power of L₁ = 4x

Power of L₂ = 1x

We know that power is the reciprocal of focal length.

∴ Focal length of L₁ = 1/4x

∴ Focal length of L₂ = 1/x

Ratio of focal lengths ;

➝ f₁ : f₂ = 1 : 4

Answer 2

Answer:

• The ratio of the focal length of A and B is 1 : 3.

Explanation:

Given that:

• The power of lenses A and B are in the ratio 3 : 1.

To Find:

• The ratio of the focal length of A and B.

Let us assume:

• Focal length of A = F
• Focal length of B = f

Formula used:

• Power = 1/(Focal length)
• Focal length = 1/(Power)

Finding the ratio of their focal length:

(Focal length of A) / (Focal length of B) = {1/(Power of A)} / {1/(Power of B)}

⇒ F/f = (1/3) / (1/1)

⇒ F/f = (1 × 1)/(3 × 1)

⇒ F/f = 1/3

⇒ F : f = 1 : 3