Which lens is used as a magnifying glass - convex lens or concave lens?

Select the correct alternative from those given below each statement and write the completed statement :

The power of a convex lens is $+4 \mathrm{D}$, then its focal length will be ______.

A point source $O$ is placed at a distance of $12.5 \mathrm{cm}$ from a converging lens of focal length $10 \mathrm{cm}$, on its principal axis as shown in the figure. Find the distance at which a diverging mirror of focal length $20 \mathrm{cm}$ should be placed, so that a real image is formed on the source itself.

A needle placed $45 \mathrm{cm}$ from a convex lens, forms an image on a screen placed $90 \mathrm{cm}$ on the other side of a lens. Determine its focal length. What is the size of the image if the object is $5 \mathrm{cm}$ ?

Draw Ray diagram to show the formation of an image when the object is placed between ${\mathrm{F}}_1$ and $2{\mathrm{F}}_1$ of a convex lens.

Draw a ray diagram to show the formation of an image when an object is placed between focus $\left({\mathrm{F}}_1\right)$ and optical centre $\left(\mathrm{O}\right)$ of a convex lens.

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.

If the Magnification produced by a Convex Lens is $-1.5$, what would be the position and nature of the image.

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.