If an object is placed between two plane mirrors inclined at an angle of $45^{\circ}$,then the number of images formed will be $9$. State whether this statement is True or False.

What are the advantages and disadvantages of using a convex mirror for seeing traffic at the rear?

Where should an object be placed in front of a convex lens to obtain an image on the same side as the object?

$(a)$ Draw a ray diagram in each of the following cases to show the position and nature of the image formed when the object is placed:
$(i)$ between optical centre and principal focus $(F)$ of a convex lens.
$(ii)$ between $F$ and $2F$ of a convex lens.
$(iii)$ at $2F$ of a convex lens.
$(b)$ How will the nature and position of the image formed change in case $(i)$ and $(ii)$ in part $(a)$ of this question if the lens is replaced by a concave lens? Draw the corresponding ray diagram.

What is the $SI$ unit of the power of a lens?

Which of the following can produce a magnification of $+5$ as well as $-5$?