The magnification produced by a plane mirror is $+1$. What does this mean?

An object $5 \,cm$ in length is held $25 \,cm$ away from a converging lens of focal length $10 \,cm$. Find the position,size,and the nature of the image formed.

$A$ spherical mirror and a thin spherical lens have each a focal length of $-15\,cm$. The mirror and the lens are likely to be

Name the type of mirror used in the following situation.
Support your answer with a reason.
$(a)$ Headlights of a car

We wish to obtain an erect image of an object,using a concave mirror of focal length $15\, cm$. What should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.

One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.