FRANCOISE SAUZE / SCIENCE PHOTO LIBRARY FRANCOISE SAUZE / SCIENCE PHOTO LIBRARY
Man using a thermochromic strip thermometer. The thermometer consists of a row of patches which change colour at different temp- eratures. Each patch has a coating of micro- encapsulated liquid crystals, whose rod-shaped molecules are arranged like the steps of a spiral staircase. At room temperature the spiral is in a compressed form and does not reflect light. As the temperature increases, the spiral expands & begins to reflect light at specific wavelengths. The composition of the crystal determines its acti- vation temperature. In this case the thermometer indicates a temperature of 38 degrees centigrade (slightly higher than normal).
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