Question

you have two lenses A and B of focal lengths +10 cm and -10 cm respectively. state the nature and power of each lens. whicj of the two lenses will form a virtual and magnified image of an object placed 8 cm from the lens ? draw a ray diagram to justify the answer.

Answer 1

virtual and magnified image will be formed by the converging lens means convex lens.
if the object is placed between lens and focal length of convex lens the image will be formed behind 2f2 and virtual and magnified.

Answer 2

Given:
FOR LENS A:
f=+10cm
P=1/f (in metres)
P=100/f ( in cm)
P=100/10
=10 dioptres.
P=+10D.
Here, + sign indicates that given lens A is converging or Convex lens.
FOR LENS B:
f=-10cm
P=100/f (in cm)
P= 100/-10
=-10dioptres.
P= -10D
Here, negative sign indicates it is concave or diverging lens.
Lens A that is Convex lens will form virtual, magnified image when object is placed at 8cm ( in between Optic centre and Focus)
Please refer the attachment for Ray diagram.