Question

calculate two possible distance of an object from a convex lens of focal length 20 CM so as to obtain an image of double the size of an image​

Answer 1

Answer:

=20cm

m=−2(red)

v=2u

Sign convention

u=−ve

v=+ve

f=+ve

Using lens formula,

v

1

−

u

1

=

f

1

⇒

−2u

1

−

u

1

=

f

1

→u=−

2

3f

=−

2

3×10

=−15cm

Object should be placed at 15cm in front of the lens.