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?
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Solution
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(a)
f=25cm
least distance of distance vision, d=25cm
closed object distance is u.
Image distance v=−d=−25cm.
1v−1u=1f⇒u=−4.167≈−4.2 Hence closest distance to resd book is 4.2 cm
for the farthest distance, v=∞
1v−1u1=1f⇒u1=−5
Hence the farthest distance at which person can read the book is 5cm.
(b)
maximum
angular magnification,
α=d/|u|=25/|−4.167|=6
minimum
angular magnification,
α=d/|u1|=25/|5|=5
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Similar Questions
Q1
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?