Question

Answer the following question in detail.

How does magnifying power differ from linear or lateral magnification?

Answer 1

1. The linear magnification is the ratio of the size of the image to the size of the object.
2. When the distances of the object and image formed are very large as compared to the focal lengths of the instruments used, the magnification becomes infinite. Whereas, the magnifying power is the ratio of the angle subtended by the object and image, gives the finite value.
3. For example, in the case of a compound microscope,
   M_min = `"D"/"f"=25/5` = 5 and M_max = `1+"D"/"f"` = 6
   Hence image appears to be only 5 to 6 times bigger for a lens of focal length 5 cm.
   For M_min = `"D"/"f"` = 5, v = ∞
   ∴ Lateral magnification (m) = `"v"/"u"` = ∞
   Thus, the image size is infinite times that of the object but appears only 5 times bigger.