UPSC NDA I 2021 General Ability Solved Paper

CONCEPT:
Sign convention in mirrors - All distances are measured from the pole of the mirror.
- The distance measured from the pole (p) to the left side of the mirror is taken as negative.
- The distance measured from the pole (p) to the right side ofthe mirror is taken as positive.
- The heights measured upwards and perpendicular to the principal axis of the mirror is taken as positive.
- The heights measured downwards and perpendicular to the principal axis of the mirror is taken as negative.
EXPLANATION:
- Mirror Formula: The following formula is known as the mirror formula, which provided a relationship between focal length (f), image distance (v), and objects distant (u) as shown below
⇒‌

1

f

=‌

1

v

+‌

1

u

- The above formulais valid for spherical mirrors only.