The Total solution for NCERT class 6-12
A man with normal nearpoint (25 cm) reads a book with small print using a magnifying glass: a thinconvex lens of focal length 5 cm.
(a) What is the closest andthe farthest distance at which he should keep the lens from the page so that hecan read the book when viewing through the magnifying glass?
(b) What is the maximumand the minimum angular magnification (magnifying power) possible using theabove simple microscope?
(a) Focal length of themagnifying glass, f = 5 cm
Least distance of distance vision, d= 25 cm
Closest object distance = u
Image distance, v = −d =−25 cm
Hence, the closestdistance at which the person can read the book is 4.167 cm.
According to the lensformula, we have:
Hence, the farthestdistance at which the person can read the book is
5 cm.
(b) Maximum angular magnification is given by therelation:
Minimum angularmagnification is given by the relation: