Question

A toy insect viewer for kids consists of a plastic container with a lens in the lid. The lid is 12 cm from the bottom of the container. The lens produces a magnified image of an insect on the bottom of the container. If the magnification is 4.0, what is the focal length of the lens? Please provide a model (ray model of light), and sketch a diagram showing the lens or mirror, the object, object distance, the image, the image distance, the focal point, and the focal length.

Answer 1

Solution:

Given,

Object distance

magnification

Let the image distane be v.

The magnification for a lens is given by,

By lens formula,

  

The lens is a convex lens. When the object is between optical centre and focus, convex lens produces a magnified virtual image.