Q30 of 51 Page 345

At what distance should the lens be held from the figure in Exercise 9.29 in order to view the squares distinctly with the maximum possible magnifying power?

Given:


Image distance, v = −d = −25 cm


Focal length, f = 10 cm


Object distance = u


When the image is formed at the near point or at the minimum distance of distinct vision, we get the maximum possible magnification.


Applying the lens formula we have:


…(1)


Where, f0 = focal length of the objective lens


v0 = Distance of image formation


u0 = Distance of object from objective


Putting values in the equation (1) we get,


⇒


⇒ u = -50/7


⇒ u = -7.14 cm


Hence, the lens should be kept 7.14 cm away in order to view the squares distinctly.


More from this chapter

All 51 →
28

A man with normal near point (25 cm) reads a book with small print using a magnifying glass: a thin convex lens of focal length 5 cm.

(a) What is the closest and the farthest distance at which he should keep the lens from the page so that he can read the book when viewing through the magnifying glass?


(b) What is the maximum and the minimum angular magnification (magnifying power) possible using the above simple microscope?

 29

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 focal length 9 cm) held close to the eye.

(a) What is the magnification produced by the lens? How much is the area of each square in the virtual image?


(b) What is the angular magnification (magnifying power) of the lens?


(c) Is the magnification in (a) equal to the magnifying power in (b)? Explain.

 30

What is the magnification in this case?

 30

Is the magnification equal to the magnifying power in this case? Explain.