Question

the linear magnification of a convex lens is -1 for the position of object at.. a- infinity
b- F1
c- 2F1
D-none of these

Answer 1

The linear magnification of a convex lens is -1 for the position of object at

1. infinity
2. F₁
3. 2F₁
4. none of these.

answer : option (3) 2F₂

explanation : magnification is the ratio of size of image to the size of object.

for lens,

  magnification. m = size of image/size of object

given, m = -1

∴ size of image/size of object = -1

⇒ size of image = - size of object

it indicates that image is real and inverted and its size is equal to the size of the object.

and we know, this is possible only when object is placed at the centre of curvature of the convex lens. i.e., 2F₁

therefore the position of object is at 2F₁