If the magnification $m$ of an image formed by a spherical mirror is negative,what is the nature of the image?

The magnification equation is a relation between image distance and object distance.

Where will the image be formed by a concave mirror when an object is placed between the pole and the focus point of the mirror?

Explain why the word $AMBULANCE$ is written in reverse on the front of some vehicles.

$(a)$ Define the optical centre of a spherical lens.
$(b)$ You are given a convex lens of focal length $30 \, cm$. Where would you place an object to get a real,inverted,and highly enlarged image of the object? Draw a ray diagram showing the image formation.
$(c)$ $A$ concave lens has a focal length of $20 \, cm$. At what distance from the lens should an object be placed so that it forms an image at $15 \, cm$ away from the lens?

What is the speed of light waves in a vacuum in units of $km/s$?