Available online
Description
The programme tries to show that there is basically no contradiction between the wave and the particle models of light and that both have to co-exist as useful analogues.
The programme tries to show that there is basically no contradiction between the wave and the particle models of light and that both have to co-exist as useful analogues.
| Module code and title: | S101, Science: a foundation course |
|---|---|
| Item code: | S101; 09 |
| First transmission date: | 01-05-1979 |
| Published: | 1979 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:24:00 |
| + Show more... | |
| Producer: | John Stratford |
| Contributors: | Stuart Freake; Keith Hodgkinson |
| Publisher: | BBC Open University |
| Keyword(s): | Ripple tank |
| Subject terms: | Diffraction; Interference (Light); Light; Wave theory of light; Particle beams |
| Footage description: | Stuart Freake introduces the programme. Keith Hodgkinson begins a demonstration of the photo-electric effect. He first irradiates a piece of zinc which is attached to an electroscope with red light of varying intensity including a powerful laser. No loss of charge is recorded by the instrument. He then irradiates the zinc with a weak ultra violet light source and an immediate loss of charge is recorded. Freake and Hodgkinson demonstrate that the photo-electric effect works only if ultra-violet rather than red light is used. Freake and Hodgkinson go on to explain, with the aid of animations and a board with counters, why ultra-violet but not red light will produce the photo-electric effect. Keith Hodgkinson demonstrates a practical application of the photo-electric effect. He has with him in the studio an apparatus in which solar cells provide the power for lifting a weight. With the aid of an animation, he explains how a solar cell works. Stuart Freake demonstrates some of the properties of waves in a ripple tank. He shows first the effect of a single slit on the propagation of waves and then the effects of a double slit. Hodgkinson demonstrates that the effects observed in the ripple tank above are also apparent in laser optical interference experiments. He produces double slit interference patterns on a screen. Going back to the ripple tank, Stuart Freake explains how waves in interference patterns combine. The waves are shown in greater detail on an oscilloscope screen. Freake points out the areas of constructive and destructive interference. Hodgkinson demonstrates an alternative method for creating optical interference patterns other than by using a double slit. For this method he places together two glass plates but in such a way that they don't quite match. An animation, with comment by Hodgkinson, explains how the interference patterns are created. Stuart Freake demonstrates a useful application of this technique - testing of optical lenses during manufacture. Keith Hodgkinson outlines an experiment which demonstrates that light, when diffracted, has the properties of a wave but also maintains its particulate properties on detection. Hodgkinson points out the equipment used for the experiment. Hodgkinson and Freake perform the experiment. They explain what is happening throughout. Keith Hodgkinson sums up the programme. |
| Master spool number: | 6HT/72985 |
| Production number: | 00525_1339 |
| Videofinder number: | 1184 |
| Available to public: | no |
