Question

A linear object of size 1.5cm placed at 10cm from a lens of focal length 20cm. The optic centre of lens and the object are displaced a distance `Delta`. The magnification of the image formed is m (Take optic centre as origin). The coordinates of image of A and B are `(x_(1),y_(1))` and `(x_(2),y_(2))` respectively. Then

A. `(x_(1),y_(1))=(-20cm, -1cm)`
B. `(x_(2),y_(2))=(-20cm, 2cm)`
C. `m=3`
D. `m=2`

Answer 1

Correct Answer - a.,b.,d.
`u=-10cm, f=20cm`
`(1)/(u)-(1)/(v)=(1)/(f)`
`(1)/(v)=(1)/(20)-(1)/(20)=(1-2)/(20)=(-1)/(20)rArrv=-20cm`
Magnification `m=(v)/(u)=(-20)/(-10)=2`
Height of image `=1.5xx2=3cm`
The `y_(1)` coordinate of a point A on the image will be
`y_(1)=(0.5)xx2=-1cm`
The `y_(2)` coordinate of a ppoint B on the image will be
`y_(2)=1xx2=2cm`