Question

Help !

An object is at a distance of 3 centimeters from a lens with a focal length of 1 centimeter. The lens creates an image on the same side of the object. What kind of lens is this? What is the image location? Is the image real or virtual?

Answer 1

Answer:

Biconcave lens or Diverging lens.

Virtual Image

0.75cm on the same side as the object.

Explanation:

Biconcave lens. Biconcave lenses form all images at the same side as the object. Although a biconvex lens can exhibit the same phenomena, it only occurs when the object is in between the focal point and the optical center (object distance<focal length). From the given parameters, the object distance is 3cm and the which is obviously greater than the focal length.

So, we conclude that the lens used is a biconcave lens.

A concave lens (biconcave, plano-convex,) alway produces a virtual image.

Let u, v and f represent the object distance, image distance and focal length of the lens respectively.

In this case,

u = 3cm

v = ?

f = -1cm ( f is negative for diverging lenses)

1/f = (1/u) + (1/v)

-1 = (1/3) + (1/v)

v = -3/4cm = -0.75 cm

The negative sign means that it's a virtual image.