The thickness of centre part of a thick lens is not negligible.

A virtual, diminished image is formed when an object is placed between the optical centre and the principal focus of a lens.
(i) Name the type of lens which forms the above image.
(ii) Draw a ray diagram to show the formation of the image with the above stated characteristics.  

What is the relation between the refractive index of water with respect to air $\left({}_{a }\mu _w\right)$, and the refractive index of air with respect to water $\left({}_{w }\mu _a\right)$.

If the refractive index of water with respect to air (${}_{a }\mu _w$)  is $\frac{5}{3}$.  Calculate the refractive index of air with respect to water (${}_{w }\mu _a$).

An object is placed at a distance $24 \mathrm{cm}$ in front of a convex lens of focal length $8 \mathrm{cm}$.
(i) Calculate the distance of the image from the lens.
(ii) Calculate the magnification of the image.