Question

For the diagram shown below, identify the correct statement regarding object (AB), lens and image (A'B'). Assume that the size of object and image is same.

• A. Point $B$, its image $B^{\prime }$ and optical centre $\left(O\right)$ of the lens are collinear.
• B. Point $B$, its image $B^{\prime }$ and optical centre $\left(O\right)$ of the lens are non- collinear.
• C. $B^{\prime }$ is the point on the virtual image of the object.
• D. None of the above

Answer 1

The correct option is A Point $B$, its image $B^{\prime }$ and optical centre $\left(O\right)$ of the lens are collinear.

Due to the parallel slab nature of the thin lens at the middle, the ray goes undeviated on passing from the optical centre (O).


Thus, point $B,O$ and $B^{\prime }$ lies on a straight line, and hence they are collinear.
Since, image $A^{\prime }{B}^{\prime }$ is formed due to real intersection of refracted rays, it is a real and inverted image.

$\begin{array}{c}\text{Why this question}?\\ \text{Bottom line: Always remember that a ray emerging}\\ \text{from object and passing through optical centre of}\\ \text{lens will be a straight line, i.e it doesn't suffer deviation}\end{array}$