Question

What is the nature of the lens and the position of the object if the image formed is of the same size as that of the object?

• A. concave lens, at 2F₁
• B. convex lens, at 2F₁
• C. concave lens, at F₁
• D. convex lens, at F₁

Answer 1

The correct option is B

convex lens, at 2F₁

From the ray diagram,

When the object is kept at '$2F_1$' (i.e., u = 2f), image formed will be real and inverted.

Object distance (u) = - 2f

Image distance (v) = 2f

Linear magnification (m) = $\frac{Heightofimage}{Heightofobject}=\frac{v}{u}$

$\Rightarrow \frac{H_i}{H_o}=\frac{-2f}{2f}=-1$

$\Rightarrow H_i=-H_o$

Hence, height of the object is equal to the height of the image.