Question

please answer this question

Answer 1

Answer:

b) 1:4

Explanation:

let power of lens L₁ be P₁ and focal length be f₁

and power of lens L₂ be P₂ and focal length be f₂

Power(P) of a lens is defined as reciprocal of focal length(f) in metres.

⇒ P ∝ 1/f

⇒ P₁/P₂ = f₂/f₁

given that, ratio of powers(P₁/P₂) = 4:1 = 4/1

⇒ 4/1 = f₂/f₁

⇒ f₂/f₁ = 4

⇒ f₁/f₂ = 1/4 = 1:4

∴ The ratio of the focal length of L₁ and L₂ is 1:4