TS EAMCET 9-Sep-2020 Shift 2 Solved Paper

For a lens, Magnification =‌

‌ Size of image ‌

‌ Size of object ‌

=‌

v

u

⇒‌‌m=‌

I

0

=‌

v

u

Here, m=±4
For m=−4,−4=‌

v

u

⇒v=−4u
Now by lens formula,
So, object is at a distance of 25cm from lens when image is real.
For, m=+4,+4=‌

v

u

⇒v=4u
Again from lens formula,
‌

1

v

−‌

1

u

=‌

1

f

⇒‌‌‌

1

4u

−‌

1

u

=‌

1

20

;⇒‌

−3

4u

=‌

1

20

or u=‌

−3

4

×20=−15cm
So, object is at a distance of 15cm from the lens, when image is virtual.