Wavelength and penetration. | Physics Forums
Penetration depth is a measure of how deep light or any electromagnetic radiation can . Relationships between these and other ways of specifying the decay of an electromagnetic field are will also have a penetration depth of 16 wavelengths, however in this case the wave will be perfectly reflected from the material!. Infrared light, which lies beyond the longer red wavelengths of visible light, was the first . The relationship between the energy of an electromagnetic wave and its The high penetration depths of these powerful waves, coupled with their. Thank you for A2A: Note that each EM wave has a wavelength. Next note that How do short wavelength electromagnetic waves penetrate matter? Views Is there any relation between matter waves and electromagnetic waves?.
Presented in Figure 4 are various waveforms representing common states that are utilized to describe the degree of uniformity of electromagnetic radiation. Because visible light is the most commonly discussed form of radiation, the examples illustrated in Figure 4 are representative of wavelengths in this spectral region.
For example, monochromatic light consists of waves all having the same wavelength and frequency, or macroscopically, the same color in visible light. In contrast, polychromatic visible light usually appears as white due to contributions from the mixture of all or most wavelengths in the spectrum ranging between and nanometers.
When light is non-polarized Figure 4the electric field vectors vibrate in all planes lying perpendicular to the direction of propagation. Light that has been reflected from a smooth surface at a critical angle, or passed through polarizing filters, assumes a plane-polarized orientation with all of the electric vectors vibrating in a single plane perpendicular to the direction of propagation. Light from the sun, and a majority of the common incandescent and fluorescent visible light sources, is non-polarized, while light seen through polarizing lenses of custom sunglasses is polarized in the vertical direction.
In some instances, light can be elliptically or circularly polarized when it passes through materials that have more than one refractive index birefringent or doubly refracting substances.
Most artificial and natural light sources emit non-coherent light that displays a variety of phase relationships among the wavelengths present in the spectrum Figure 4. In this case, the peaks and valleys of the vibrational states in individual waves do not coincide in either space or time. Coherent light is composed of wavelengths that are in phase with each other, and behaves in a very different manner than non-coherent light with respect to the optical properties and interaction with matter.
Wavefronts produced by coherent light have electric and magnetic vector vibrations that oscillate in phase, have low divergence angles, and are usually composed of monochromatic light or wavelengths that have a narrow distribution.
Electromagnetic Radiation - The Nature of Electromagnetic Radiation
Lasers are a common source of coherent light. Light waves that have coaxial, relatively non-diverging paths as they travel through space are termed collimated. This organized form of light does not spread or converge to a significant degree over comparatively long distances. Collimated light forms a very tight beam, but does not necessarily have a narrow band of wavelengths nor must it be monochromatica common phase relationship, or a defined state of polarization.
Wavefronts of collimated light are planar and perpendicular to the axis of propagation. In contrast, divergent or non-collimated light spreads to varying degrees while traveling through space, and must be passed through a lens or aperture in order to be collimated or focused.
Gamma rays - High-energy radiation that possesses the highest frequency and shortest wavelengthsgamma rays are emitted as the result of transitions within the atomic nucleus, including nuclei of certain radioactive materials natural and artificial. Gamma waves also originate from nuclear explosions and a variety of other sources in outer space.
These powerful rays possess tremendous penetrating ability and have been reported to be able to pass through three meters of concrete! Individual gamma-ray photons contain so much energy that they are easily detected, but the extremely small wavelength limits the experimental observation of any wavelike properties.
Gamma rays originating from the hottest regions of the universe, including supernova explosions, neutron stars, pulsars, and black holes, travel through vast distances in space to reach the Earth.
This high-energy form of radiation has wavelengths less than one-hundredth of a nanometer 10 picometersphoton energies greater than kiloelectron-volts keVand frequencies exceeding 30 exahertz EHz.
Exposure to gamma rays can induce mutations, chromosome aberrations, and even cell death, as is often observed in some forms of radiation poisoning. However, by controlling the emission of gamma rays, radiologists can re-direct the high energy levels to combat disease and help cure some forms of cancer.
Gamma ray astronomy is a relatively new science that collects these high-energy waves in order to produce images of the universe, as illustrated in Figure 5. This technique affords scientists opportunities to observe distant celestial phenomena in the search for new physical concepts, and to test theories that cannot be challenged by experiments performed here on the Earth.
X-rays - Electromagnetic radiation having a frequency just above the ultraviolet but below the gamma range is classified as X-rays, and is energetic enough to pass easily through many materials, including the soft tissues of animals.
The high penetration depths of these powerful waves, coupled with their ability to expose photographic emulsions, has led to the extensive use of X-rays in medicine to investigate textures in the human body, and in some cases, as a therapeutic or surgical tool. In the same manner as higher-energy gamma rays, uncontrolled exposure to X-rays can lead to mutations, chromosome aberrations, and other forms of cell damage.
Traditional radiographic imaging methods essentially produce nothing more than shadow castings of dense material, rather than detailed images.
Recent advances in X-ray focusing technique using mirror optics, however, has led to significantly more detailed imagery from a variety of objects utilizing X-ray telescopes, X-ray microscopes, and interferometers.
Hot gases in outer space emit a powerful spectrum of X-rays, which are utilized by astronomers to gain information about the origin and characteristics of interstellar regions of the universe. Many extremely hot celestial objects, including the sun, black holes, and pulsars, emit primarily in the X-ray region of the spectrum and are the subjects of astronomical X-ray investigations.
electromagnetic radiation - Penetration versus Frequency - Physics Stack Exchange
The frequency spectrum of X-rays spans a very large range with the shortest wavelengths approaching the diameter of an atom. However, the entire X-ray spectral region traverses the length scale between approximately 10 nanometers and 10 picometers.
This wavelength range makes X-ray radiation an important tool to geologists and chemists for characterizing the structure and properties of crystalline materials, which have periodic structural features on a length scale comparable to the X-ray wavelengths.
Ultraviolet Light - Often abbreviated uvultraviolet radiation propagates at frequencies just above those of violet in the visible light spectrum. Although the low-energy end of this spectral region is adjacent to visible light, ultraviolet rays at the upper end of their frequency range have enough energy to kill living cells and produce significant tissue damage.
The sun is a constant source of ultraviolet radiation, but the atmosphere of the Earth primarily ozone molecules effectively blocks a majority of the shorter wavelengths of this potentially lethal radiation stream, thus affording a suitable living environment for plants and animals. Photon energies in the ultraviolet are sufficient to ionize the atoms from a number of gas molecules in the atmosphere, and this is the process by which the ionosphere is created and sustained.
Although small doses of this relatively high-energy light can promote the production of vitamin D in the body, and cause minimal tanning of the skin, too much ultraviolet radiation can lead to serious sunburn, permanent retinal damage, and the promotion of skin cancer. Ultraviolet light is utilized extensively in scientific instruments to probe the properties of various chemical and biological systems, and it is also important in astronomical observations of the solar system, galaxy, and other parts of the universe.
Stars and other hot celestial objects are strong emitters of ultraviolet radiation. The ultraviolet wavelength spectrum ranges from about 10 to approximately nanometers, with photon energies ranging between 3.
At longer wavelengths, there is no corresponding energy level for the EM radiation, thus the wave passes through the body. This is not strictly correct. If the absorption of radiation was strictly due to atomic energy levels then the absorption would occur only at very narrow bandwidths, which is contrary to common experience like the black body radiator for example or microwave heating.
The phonons in a material will absorb radiation over a larger bandwidth than the atoms alone. As Bob S stated, the penetration of high energy waves actually increases with shortening of wavelength.
The absorption properties of a material will greatly vary over the frequency range. In general, I would only say that high energy waves will pass through most objects largely unimpeded.
Below x-rays, the absorption becomes widely varying and material dependent.
For example, water is transparent in the visible light region for most purposes let's say but it is much more highly absorptive in the infrared and microwave region. So for water, over a given bandwidth, the absorption decreases as the wavelength decreases.