video record
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Description
The programme develops the basic theoretical ideas of Fourier analysis within the framework of diffraction.
Metadata describing this Open University video programme
Module code and title: ST291, Images and information
Item code: ST291; 03
First transmission date: 24-03-1977
Published: 1977
Rights Statement:
Restrictions on use:
Duration: 00:23:37
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Producer: Ted Smith
Contributors: Barrie Jones; Alan Walton
Publisher: BBC Open University
Keyword(s): Cosines; Diffraction patterns; Fourier Series; Laser arrangement analogues
Footage description: Shots of a laser diffraction pattern derived from a simple cosinusoidal grating. Barrie Jones introduces the programme. Alan Walton adds three diffraction gratings of different spatial frequency together and comments on the results. Barrie Jones builds up a square wave form on an oscilloscope screen by adding together several cosinusoidal wave forms of different frequency. Alan Walton summarises the results of Jones' experiment above by examining the equations for the synthesis and then by showing a graph. He explains how the data for the graph is obtained. Barrie Jones goes on to generate a triangular wave-form on the oscilloscope. Alan Walton, using several graphic aids, compares the data for square waves with that for triangular wave. Barrie Jones examines the interaction between waves and gratings. He uses a ripple tank, to generate plane waves, passes these through plastic square wave gratings and observes the resulting diffraction. Alan Walton uses an oscilloscope to represent the conditions at the output side of the square gratings in the above ripple tank experiment. He demonstrates that the output wave can be represented as the sum of two other waves - a standing wave and a straight line. Barrie Jones then represents the straight line component with a plastic model. He points out and explains the component parts of the model. Alan Walton, still using an oscilloscope, demonstrates a method of representing a standing wave by running two travelling, cosinusoidal waves together. Barrie Jones manipulates his model to demonstrate how two running waves, as shown in Alan's demonstration above, are obtained at the gratings. Walton and Jones sum up. Jones explains how the laser diffraction pattern shown at the start of the programme is accounted for in terms of cosinusoidal components studied in the programme.
Master spool number: HOU2246
Production number: 00525_1243
Videofinder number: 2114
Available to public: no