CBSE Class 10 Science 2020 · Paper 31(B) · Question 21

(a) Principal focus: rays of light parallel to the principal axis, after reflection from a concave mirror, meet at a point on the principal axis; this point is the principal focus of the concave mirror. For an erect image the object must be placed between the pole and the principal focus, that is, at a distance of less than $12$ cm from the mirror ($0<|u|<12$ cm). The image is then virtual, erect and enlarged. (b) (i) A convex mirror always forms an erect, though diminished, image of the vehicles behind. (ii) Being curved outwards, it has a wider field of view, so the driver can see a much larger area of the traffic behind.