Principle
A zone plate is illuminated with parallel laser light. The focal points of several orders of the zone plate are projected on a ground glass screen.
Benefits


find out that optical lenses can be completely different from what you are used to

interference is used to produce effects commonly achieved with diffraction

the use of a laser lightsource provides clear results



Tasks

The laser beam must be widened so that the zone plate is well illuminated. It must be assured that the laser lightbeam runs parallel over several meters.
The focal points of several orders of the zone plate are projected on a ground glass screen. The focal lengths to be determined are plotted against the reciprocal value of their order.
The radii of the zone plate are calculated.

What you can learn about

Huygens Fresnel principle
Fresnel and Fraunhofer diffraction
Interference
Coherence
Fresnel’s zone construction
Zone plates