Question

According to Cartesian sign convention, which of the following is/are true?

• A. The focal length of the concave mirror is positive and the focal length of the convex mirror is negative.
• B. The focal length of the concave mirror is negative and the focal length of the convex mirror is positive.
• C. All distances are measured from the pole of the mirror.
• D. The focal length of the concave mirror and the convex mirror is negative.

Answer 1

Answer: (B), (C)

The correct options are
B

The focal length of the concave mirror is negative and the focal length of the convex mirror is positive.

C

All distances are measured from the pole of the mirror.

According to Cartesian sign convention,

• All distances are measured from the pole of the mirror.
• The distances measured along the direction of incident light are considered positive
• The heights measured upward and normal to the principal axis are taken as positive.

f, the focal length, is positive for a concave mirror, and negative for a convex mirror. When the image distance is positive, the image is on the same side of themirror as the object, and it is real and inverted. When the image distance is negative, the image is behind the mirror, so the image is virtual and upright