Question
A card sheet divided into squares each of size 1 mm2 is being viewed at a distance of 9 cm through a magnifying glass (a converging lens of focl length 10 cm) held close to the eye.
Is the magnification equal to the magnifying power in this case? Explain.
Solution
No. Magnification of an image by a lens and angular magnification (or magnifying power) of an optical instrument are different from each other.
Angular magnification is the ratio of the angular size of the image (even if the image is magnified) to the angular size of the object if placed at the near point (25 cm).
Thus, magnification magnitude = and,
Magnifying power is
Only when the image is located at the least distance of distinct vision, we can have both the quantities equal.
Angular magnification is the ratio of the angular size of the image (even if the image is magnified) to the angular size of the object if placed at the near point (25 cm).
Thus, magnification magnitude = and,
Magnifying power is
Only when the image is located at the least distance of distinct vision, we can have both the quantities equal.
