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

The velocity of light in a vacuum is $....$

What is meant by power of a lens? Define its $SI$ unit. You have two lenses $A$ and $B$ of focal lengths $+10\, cm$ and $-10\, cm$ respectively. State the nature and power of each lens. Which of the two lenses will form a virtual and magnified image of an object placed $8\, cm$ from the lens? Draw a ray diagram to justify your answer.

In which medium is the speed of light the highest?

Magnification produced by a rear-view mirror fitted in vehicles $....$

If the radius of curvature of a spherical mirror is $30 \ cm$,what is its focal length (in $cm$)?