Find the focal length of a lens of power $-2.0 \, D$. What type of lens is this?

$(a)$ $A$ thin converging lens forms a:
$(i)$ Real magnified image.
$(ii)$ Virtual magnified image of an object placed in front of it.
Write the positions of the objects in each case.
$(b)$ Draw labelled ray diagrams to show the image formation in each case.
$(c)$ How will the following be affected on cutting this lens into two halves along the principal axis?
$(i)$ Focal length,
$(ii)$ Intensity of the image formed by half lens.

Where is the image formed when an object is placed anywhere in front of a concave lens?

Is it possible for a lens to act as a convergent lens in one medium and a divergent lens in another?

What is the nature of the final image formed by an astronomical telescope compared to the object?

The ray diagram given below illustrates the experimental setup for the determination of the focal length of a converging lens using a plane mirror.
$(i)$ State the magnification of the image formed.
$(ii)$ Write two characteristics of the image formed.
$(iii)$ What is the name given to the distance between the object and the optical centre of the lens in the given diagram?