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Biophysics is the integration and application of the principles of physics to explain and explore the form and function of living things. The most familiar examples of the role of physics in biology are the use of lenses to correct visual defects and the use of x rays to reveal the structure of bones. Principles of physics have been used to explain some of the most basic processes in biology such as osmosis, diffusion of gases, and the function of the lens of the eye in focusing light on the retina.

The understanding that living organisms obey the laws of physics as non-living systems do has had profound effects on the study of biology. The discovery of the relationship between electricity and muscle contraction by Luigi Galvani, an eighteenth-century physician, initiated a field of research that had continued to give information about the nature of muscle contraction and nerve impulses. It has led to the development of such instruments and devises as the electrocardiograph, electroencephalograph, and cardiac pacemaker. Medical technology in particular has benefited from the association of physics and biology. Medical imaging with 3-D diagnostic techniques such as computer tomographic (CAT) scanning, magnetic resonance imaging and positron emission tomography have permitted researchers to look inside living things without disrupting life processes. Today, lasers and x rays are routinely used in medical treatments.

The use of non-invasive imaging traces it roots to advances in the understanding of the fundamentals and biophysical interactions of electromagnetism during the nineteenth century. By 1900, physicist Wilhelm Konrad Roentgen's (1845–1923) discovery of high energy electromagnetic radiation in the form of x rays found use in medical diagnosis. Developments in radiology progressed throughout the first half of the twentieth century, finding extensive use in the treatment of soldiers during World War II.

Although nuclear medicine—heavily based upon advances in biophysics—traces its clinical origins to the 1930s, the invention of the scintillation camera in the 1950s brought nuclear medical imaging to the forefront of diagnostics.

The use of a wide array of instruments and techniques futhered by discoveries in physics, especially electronics, has helped biology to change from a descriptive science to an analytical one. An example of this is one of the most important events of this century, deciphering the structure of the DNA molecule using x-ray diffraction, a technique which has also been used to determine the structure of hemoglobin, viruses, and a variety of other biological molecules and microorganisms. The ability to apply information discovered in physics to the study of living things led to the development and use of the electron microscope and ultracentrifuge, instruments that have revealed much information about cell structure and function. Other applications have been sensors for heat and pressure detection that give information about body functions under a variety of conditions which have been of great importance in the space program.

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Science EncyclopediaScience & Philosophy: Bilateral symmetry to Boolean algebra