A doctor examines a mole with a 15.0 cm focal length magnifying glass held 12.4 cm from the mole. a. What is its magnification?
b. Where is the image?
c. How big is the image of a 5.00 mm diameter mole?

a. Magnification = 6.1

b. The image formed is virtual, and on the same side of the lens as the object.

c. Image size = 119.8 squared millimetres

Explanation:

Magnification =

But, focal length, f = 15.0 cm, and object distance, u = 12.4 cm. Let the image distance be represented by v.

a. Applying the lens formula, we have;

= +

= +

= -

  = -

v = -75.1538

The image distance, v = -75.2 cm

Magnification =

                       = 6.0645

Magnification = 6.1

b. The image formed is virtual, and on the same side of the lens as the object.

c. Given that diameter of mole = 5.00 mm.

Its radius = =

              = 2.5 mm

Thus, the area of the mole would be;

A =

   = x

   = 19.643

A = 19.64 square millimetres.

Thus, the size of the image can be determined by;

Magnification =

Image size = Magnification x object size

                  = 6.1 x 19.64

                  = 119.804

The size of the image is 119.8 squared millimetres.