Question

A man with a normal near point of 25cm reads a book of small font using a magnifying glass whose focal length is 5 cm. What is the closest and the farthest point from which he can read the book

Answer 1

$\huge\red{Answer }$

 

Solution :

given f=5cmf=5cm

v=−25cmv=−25cm

1f=1v−1u1f=1v−1u

1u=1v−1f1u=1v−1f

1u=1−25−151u=1−25−15

=−1−525=−1−525

∴u=−256∴u=−256

=−4.2cm=−4.2cm

This is the closest distance he can read the book. for the farthest distance ,

v′=∞v′=∞

1f=1v′1f=1v′

∴1u′=1v′−1f∴1u′=1

HOPE IT HELPS YOU !!