Question

(a) The magnification is positive for all virtual images and is negative for all real images.

(b) The magnification of the concave lens and convex mirror is always positive whereas the magnification of the convex lens and concave mirror can be positive or negative depending on the position of the object before the lens.

• A. Only (a) is true
• B. Only (b) is true
• C. Both (a) and (b) are true
• D. Both (a) and (b) are false

Answer 1

The correct option is C

Both (a) and (b) are true

Magnification

1. Magnification is the enlargement in the image size produced by rounded mirrors as matched to the object size.
2. It is the ratio of the height of the image to the height of the object and is denoted as m.
3. The magnification, m produced by a spherical mirror can be expressed as: $m={\raisebox{1ex}{$h$}\!\left/ \!\raisebox{-1ex}{$h$}\right.}^{\text{'}}$, here, $h$ is the height of the image and $h\text{'}$ is the height of the object.
4. The height of the object is always positive because we are considering the object is always above the principal axis.
5. Virtual image's height should be taken as positive while the real image's height should be taken as negative.
6. The positive magnitude of magnification is the indication of virtual and erect images.
7. The negative magnitude of magnification is the indication of a real and inverted image
8. The concave lens and the convex mirror give a virtual image. Their magnification is positive.
9. The convex lens and the concave mirror can produce real and virtual images based on the object, therefore, their magnification can be positive or negative.

Thus the correct option is option C. i.e. Both a and b are true.