Principle

The focal lengths of unknown lenses are determined by measuring
the distances of image and object and by Bessel’s method. Simple
optical instruments are then constructed with these lenses.

Tasks


To determine the focal length of two unknown convex lenses by
measuring the distances of image and object.

To determine the focal length of a convex lens and of a
combination of a convex and a concave lens using Bessel’s
method.

To construct the following optical instruments:
a) Slide projector; image scale to be determined
b) Microscope; magnification to be determined
c) Kepler-type telescope
d) Galileo’s telescope (opera glasses).


What you can learn about


Law of lenses

Magnification

Focal length

Object distance

Telescope

Microscope

Path of a ray

Convex lens

Concave lens

Real image

Virtual image

Benefits


understand a basic optical component: the lens

learn how common optical instruments work

geometric optics in a nutshell