Question

According to the New Cartesian Sign Convention for mirrors, what sign has been given to the following:

a. Height of erect and virtual image.

b. Focal length of concave mirror.

Answer 1

The explanation for part a

1. The distance measured above the principal axis is positive.
2. Hence, the height of the erect and virtual image is positive.

The explanation for part b

1. The focal length of a concave mirror is negative.
2. As the focal length of a concave mirror is measured on the left side of the pole of the mirror, along the negative x-axis, it is taken as negative.