Calcium in bones absorbs x-rays the most, so bones look white. Fat and other soft tissues absorb less and look gray. Air absorbs the least, so lungs look black. The most familiar use of x-rays is checking for fractures broken bones , but x-rays are also used in other ways.
For example, chest x-rays can spot pneumonia. Mammograms use x-rays to look for breast cancer. When you have an x-ray, you may wear a lead apron to protect certain parts of your body. Our Sun's radiation peaks in the visual range, but the Sun's corona is much hotter and radiates mostly x-rays. To study the corona, scientists use data collected by x-ray detectors on satellites in orbit around the Earth.
Japan's Hinode spacecraft produced these x-ray images of the Sun that allow scientists to see and record the energy flows within the corona. The physical temperature of an object determines the wavelength of the radiation it emits.
The hotter the object, the shorter the wavelength of peak emission. X-rays come from objects that are millions of degrees Celsius—such as pulsars, galactic supernovae remnants, and the accretion disk of black holes.
From space, x-ray telescopes collect photons from a given region of the sky. The photons are directed onto the detector where they are absorbed, and the energy, time, and direction of individual photons are recorded. Such measurements can provide clues about the composition, temperature, and density of distant celestial environments. Due to the high energy and penetrating nature of x-rays, x-rays would not be reflected if they hit the mirror head on much the same way that bullets slam into a wall.
X-ray telescopes focus x-rays onto a detector using grazing incidence mirrors just as bullets ricochet when they hit a wall at a grazing angle. Both of these techniques work best for heavier elements such as metals. This radiation was considered a nuisance because it caused the particles to lose energy, but it was later recognized in the s as light with exceptional properties that overcame the shortcomings of X-ray tubes.
One interesting feature of synchrotron radiation is that it is polarized; that is, the electric and magnetic fields of the photons all oscillate in the same direction, which can be either linear or circular.
Due to their ability to penetrate certain materials, X-rays are used for several nondestructive evaluation and testing applications, particularly for identifying flaws or cracks in structural components. The resulting shadowgraph shows the internal features" and whether the part is sound. This is the same technique used in doctors' and dentists' offices to create X-ray images of bones and teeth, respectively.
X-rays are also essential for transportation security inspections of cargo, luggage and passengers. Electronic imaging detectors allow for real-time visualization of the content of packages and other passenger items.
The original use of X-rays was for imaging bones, which were easily distinguishable from soft tissues on the film that was available at that time. However, more accurate focusing systems and more sensitive detection methods, such as improved photographic films and electronic imaging sensors, have made it possible to distinguish increasingly fine detail and subtle differences in tissue density, while using much lower exposure levels.
Additionally, computed tomography CT combines multiple X-ray images into a 3D model of a region of interest. Similar to CT, synchrotron tomography can reveal three-dimensional images of interior structures of objects like engineering components, according to the Helmholtz Center for Materials and Energy. In Heinrich Hertz and his student Philipp Lenard were generating X-rays although they probably did not know it from cathode ray tubes, and investigating their penetrating ability through different materials.
Prior to this, there is evidence to suggest that Nikola Tesla, from onwards, had worked with X-rays, and before him, from onwards, the Ukrainian-born Ivan Pulyui had already pioneered the invention and use of X-rays.
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