Question

A convex lens of focal length f is placed in between an object and a screen at a distance d

Answer 1

[mx / (m + 1)2]

Explanation:

Given: x = u + v and m = (v/u)  ∴ x = u + mu = u(m + 1)  ∴ u = [x / (m + 1)] and v = [mx / (m + 1)]  we know  (1/f) = (1/v) + (1/u)  ∴ (1/f) = [1 / {mx / (m + 1)}] + [1 / {x / (m + 1)}]  ∴ (1/f) = [(m + 1) / mx] + [(m + 1) / x]  ∴ (1/f) = [{(m + 1) + m(m + 1)} / mx]  ∴ (1/f) = [{(m + 1)(1 + m)} / mx] = [(m + 1)2 / mx]  ∴ f = [mx / (m + 1)2]

Hope this answer is correct

Answer 2

A convex lens of focal length f is placed somewhere in between an object and a screen. The distance between the object and the screen is x. If the numerical value of the magnification produced by the lens is m, then the focal length of the lens is:

(a) mx / (m+1)²

(b) mx / (m-1)²

(c) (m+1)²x /m

(d) (m-1)²x /m

hope it help you so mark my answer into brainliest ✌️✌️✌️✌️✌️✌️✌️✌️✌️ and follow me and say thank to me also