Available online
Description
The programme examines how atomic structure can be recognised inside a solid and what this regularity implies for one particular property of solids, shear.
The programme examines how atomic structure can be recognised inside a solid and what this regularity implies for one particular property of solids, shear.
| Module code and title: | ST285, "Solids, liquids and gases" |
|---|---|
| Item code: | ST285; 07 |
| First transmission date: | 05-05-1973 |
| Published: | 1973 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:21:29 |
| + Show more... | |
| Producer: | Andrew Millington |
| Contributors: | Ian Lowe; Graham Weaver |
| Publisher: | BBC Open University |
| Keyword(s): | Anisotropy; Atomic structure; Ball models; Crystal; Diffuse halo; Laser; Quartz; Wax; X-ray diffraction; Zinc |
| Footage description: | Shots of two masks composed of opaque dots which simulate molecules in array. One is in perfect array, the other in random array. Graham Weaver introduces the programme. Ian Lowe with apparatus for a laser diffraction experiment. He explains how the equipment works and then directs a laser beam at masks composed of random and regular arrays of spots. The diffraction patterns are shown on a screen. Shots of water waves striking a mask of regular pattern and being scattered in a regular defined direction. Lowe sums up this characteristic of waves. Graham Weaver explains why X-rays rather than light are used in diffraction experiments on solids. Shots of X-ray diffraction patterns from a crystal, then a piece of glass. Weaver uses the crystal diffraction photograph to explain the principles of X-ray diffraction. Weaver builds up a molecular model of a hexagonal crystal. He then holds up a piece of quartz as an example of a hexagonal crystal. Ian Lowe does an experiment to test the thermal conductivity of quartz which turns out to be anisotropic with respect to thermal conductivity. Graham Weaver uses the model of the hexagonal crystal to explain this anisotropic phenomenon in quartz. Shot of a zinc crystal and then film shots of a zinc crystal being grown. Ian Lowe explains the tensile test experiment which will be conducted on a zinc crystal. A zinc crystal is tested in a tensile testing machine. The specimen is aligned in such a way that the hexagonal planes are perpendicular to the direction of stress. The force extension curve is shown on an oscilloscope screen. Graham Weaver uses a model of a hexagonal molecule to explain why the crystal above broke so quickly. Another zinc crystal is tensile tested. This time stress is applied at an angle of 45 degrees to the axis and the crystal stretches but does not break. The force/extension curve for this experiment is shown. Graham Weaver uses a model of a hexagonal molecule to explain the above behaviour of the zinc crystal. Graham Weaver uses two models of crystal to explain why crystals only slide along certain planes. Ian Lowe with a model showing cubic crystal structure. He takes off the corners to expose the body diagonal planes where slip occurs. A cubic crystal of aluminium is tensile tested with the crystal mounted perpendicular to the body diagonal plane. The force/extension curve is shown. Ian Lowe uses a model of a cubic crystal to explain why the crystal tested above does not break. Graham Weaver with a micrograph of the surface of a crystal. He points out the markings and explains what they are. Ian Lowe uses a molecular model of a solid to demonstrate why dislocated planes slide more easily than a perfect plane. |
| Master spool number: | 6HT/70850 |
| Production number: | 00525_1031 |
| Videofinder number: | 684 |
| Available to public: | no |
