Like radio waves, microwaves, visible light and gamma rays, x-rays are part of the electromagnetic spectrum. The electromagnetic spectrum describes forms of electromagnetic radiation that propagate in wave-form. The relationship between the wavelength and energy of radiation is inverse, such that long wavelength radiation has lower energy than short wavelength radiation.
The electromagnetic spectrum starts with long-wavelength radio waves and progresses to shorter wavelength, higher energy, higher frequency waves, as shown in figure 1. Both natural and man-made objects are capable of generating electromagnetic radiation. The most familiar source is the sun, which emits all types of radiation from radio waves to high-energy x-rays and gamma rays. Hotter, higher-energy objects create higher energy radiation than cool, low-energy objects. Only extremely hot objects or particles moving at very high speed, can crate high-energy radiation such as x-rays and gamma rays.
Electromagnetic radiation has the peculiar property that it behaves both like a classic wave, and also like a particle. Thus, electromagnetic radiation can be described as either a wave with a particular wavelength, frequency and energy, or as a stream of massless particles, traveling at the velocity of light, called “photons.” The principle difference between the different types of radiation, is the amount of energy in their associated photons. Thus gamma rays and x-rays have higher energy photons than visible light or radio waves.
This energy difference is quite apparent in the interaction of electromagnetic radiation with organic matter, such as our bodies. UV radiation from the sun has higher energy than visible light and it can cause burns on our skin and damage our eyes. X-ray energy is even greater, and is sufficiently large that it can penetrate right through our bodies. Because our bodies are made up of a wide range of materials, from bone and muscle, to soft tissue and blood, we can take advantage of the penetration property of x-rays to “see” inside our bodies. Different materials absorb or transmit x-rays in varying amounts, such that x-ray sensitive films can capture x-rays passing through our bodies, creating distinct images of bones, teeth and soft tissue – which are extremely valuable for medical diagnostics and treatment.
Too much exposure to high-energy x-rays, however, is even more harmful than exposure to UV radiation. This is why medical x-ray images involve very low amounts of x-ray energy in very short bursts.
X-rays were discovered quite accidentally in 1895 by German scientist Wilhelm Conrad Roentgen, who was working with vacuum tubes. One week after their discovery, he took an x-ray image of his wife’s hand, clearly showing the bones of her fingers and her wedding ring. Understandably, this image captured the imagination of the general public and the scientific community alike, who were anxious to learn more about this new form of radiation energy.
Roentgen applied the temporary name of “x”-ray to indicate the unknown nature of this radiation. Though he subsequently objected, the name x-ray stuck, although they are often referred to as “Roentgen rays” in Germany.
Within weeks of Roentgen’s discovery, researchers around the world were duplicating his experiments and designing their own. Within only a few months, doctors in New York were already using x-rays to view broken bones and other injuries in their patients.
While medicine remains the most common use of x-rays, they are also widely used in other applications, from airport security, to industrial inspection and quality control systems. In the past 15 years, the development of x-ray optical components that manipulate x-rays in much the same way as glass lenses manipulate light, has revolutionized the application of x-ray technology into entirely new areas of research.
Xradia is a pioneering company in the field of x-ray optical components. The development of advanced x-ray lenses or so-called zone plates, makes it possible to focus an x-ray beam down to a spot as small as 30nm or about 150 atoms across! This has enabled the development of extremely high resolution x-ray microscope systems having wide application in fields from semiconductor development and inspection, to advanced materials, environmental science, nanotechnology and life sciences.
Explore our website and learn more about our 3D x-ray microscope systems and their underlying technology. Visit our image gallery to see examples of high-resolution 2D images and full 3D tomography movie-loops. Have a potential application? Contact our technical sales staff to find out more…