In humans, prolonged exposure to solar UV radiation may result in acute and chronic health effects on the skin, eye, and immune system. Moreover, UVC can cause adverse effects that can variously be mutagenic or carcinogenic.
The International Agency for Research on Cancer of the World Health Organization has classified all categories and wavelengths of ultraviolet radiation as a Group 1 carcinogen. UVB exposure induces the production of vitamin D in the skin. The majority of positive health effects are related to this vitamin. It has regulatory roles in calcium metabolism which is vital for normal functioning of the nervous system, as well as for bone growth and maintenance of bone density , immunity, cell proliferation, insulin secretion, and blood pressure.
X-rays are electromagnetic waves with wavelengths in the range of 0. They are shorter in wavelength than UV rays and longer than gamma rays. X-ray photons carry enough energy to ionize atoms and disrupt molecular bonds. This makes it a type of ionizing radiation and thereby harmful to living tissue. A very high radiation dose over a short amount of time causes radiation sickness, while lower doses can give an increased risk of radiation-induced cancer.
In medical imaging this increased cancer risk is generally greatly outweighed by the benefits of the examination. The ionizing capability of X-rays can be utilized in cancer treatment to kill malignant cells using radiation therapy. It is also used for material characterization using X-ray spectroscopy. X-Ray Spectrum and Applications : X-rays are part of the electromagnetic spectrum, with wavelengths shorter than those of visible light.
Different applications use different parts of the X-ray spectrum. X-rays with photon energies above 5 to 10 keV below 0. Due to their penetrating ability, hard X-rays are widely used to image the inside of objects e. As a result, the term X-ray is metonymically used to refer to a radiographic image produced using this method, in addition to the method itself. Since the wavelength of hard X-rays are similar to the size of atoms, they are also useful for determining crystal structures by X-ray crystallography.
In medical diagnostic applications, the low energy soft X-rays are unwanted, since they are totally absorbed by the body, increasing the radiation dose without contributing to the image. Hence, a thin metal sheet, often of aluminum, called an X-ray filter, is usually placed over the window of the X-ray tube, absorbing the low energy part in the spectrum.
This is called hardening the beam since it shifts the center of the spectrum towards higher energy or harder X-rays. The distinction between X-rays and gamma rays is somewhat arbitrary. The electromagnetic radiation emitted by X-ray tubes generally has a longer wavelength than the radiation emitted by radioactive nuclei.
Historically, therefore, an alternative means of distinguishing between the two types of radiation has been by their origin: X-rays are emitted by electrons outside the nucleus, while gamma rays are emitted by the nucleus. There is overlap between the wavelength bands of photons emitted by electrons outside the nucleus, and photons emitted by the nucleus. Like all electromagnetic radiation, the properties of X-rays or gamma rays depend only on their wavelength and polarization. Gamma rays are very high frequency electromagnetic waves usually emitted from radioactive decay with frequencies greater than 10 19 Hz.
Identify wavelength range characteristic for gamma rays, noting their biological effects and distinguishing them from gamma rays. However, this is not a hard and fast definition, but rather only a rule-of-thumb description for natural processes. Gamma rays from radioactive decay are defined as gamma rays no matter what their energy, so that there is no lower limit to gamma energy derived from radioactive decay. Gamma decay commonly produces energies of a few hundred keV, and almost always less than 10 MeV.
Gamma rays are ionizing radiation and are thus biologically hazardous. They are classically produced by the decay from high energy states of atomic nuclei, a process called gamma decay, but are also created by other processes.
Paul Villard, a French chemist and physicist, discovered gamma radiation in , while studying radiation emitted from radium during its gamma decay. Natural sources of gamma rays on Earth include gamma decay from naturally occurring radioisotopes such as potassium, and also as a secondary radiation from various atmospheric interactions with cosmic ray particles.
Some rare terrestrial natural sources that produce gamma rays that are not of a nuclear origin, are lightning strikes and terrestrial gamma-ray flashes, which produce high energy emissions from natural high-energy voltages. Gamma rays are produced by a number of astronomical processes in which very high-energy electrons are produced. Such electrons produce secondary gamma rays by the mechanisms of bremsstrahlung, inverse Compton scattering and synchrotron radiation.
Notable artificial sources of gamma rays include fission such as occurs in nuclear reactors, and high energy physics experiments, such as neutral pion decay and nuclear fusion. Gamma rays have characteristics identical to X-rays of the same frequency—they differ only in source. They have many of the same uses as X-rays, including cancer therapy. Gamma radiation from radioactive materials is used in nuclear medicine.
The distinction between X-rays and gamma rays has changed in recent decades. Originally, the electromagnetic radiation emitted by X-ray tubes almost invariably had a longer wavelength than the radiation gamma rays emitted by radioactive nuclei. However, with artificial sources now able to duplicate any electromagnetic radiation that originates in the nucleus, as well as far higher energies, the wavelengths characteristic of radioactive gamma ray sources vs.
Thus, gamma rays are now usually distinguished by their origin: X-rays are emitted by definition by electrons outside the nucleus, while gamma rays are emitted by the nucleus.
Exceptions to this convention occur in astronomy, where gamma decay is seen in the afterglow of certain supernovas, but other high energy processes known to involve other than radioactive decay are still classed as sources of gamma radiation. A notable example is extremely powerful bursts of high-energy radiation normally referred to as long duration gamma-ray bursts, which produce gamma rays by a mechanism not compatible with radioactive decay.
These bursts of gamma rays, thought to be due to the collapse of stars called hypernovas, are the most powerful events so far discovered in the cosmos. Bright spots within the galactic plane are pulsars spinning neutron stars with strong magnetic fields , while those above and below the plane are thought to be quasars galaxies with supermassive black holes actively accreting matter. All ionizing radiation causes similar damage at a cellular level, but because rays of alpha particles and beta particles are relatively non-penetrating, external exposure to them causes only localized damage e.
Gamma rays and neutrons are more penetrating, causing diffuse damage throughout the body e. The most biological damaging forms of gamma radiation occur at energies between 3 and 10 MeV. Privacy Policy. Skip to main content. Electromagnetic Waves. Search for:. The Electromagnetic Spectrum. There is a wide range of subcategories contained within radio including AM and FM radio. Radio waves can be generated by natural sources such as lightning or astronomical phenomena; or by artificial sources such as broadcast radio towers, cell phones, satellites and radar.
AM waves have constant frequency, but a varying amplitude. FM radio waves are also used for commercial radio transmission in the frequency range of 88 to MHz. FM stands for frequency modulation, which produces a wave of constant amplitude but varying frequency. Information is carried by amplitude variation, while the frequency remains constant. FM radio waves : Waves used to carry commercial radio signals between 88 and MHz. Information is carried by frequency modulation, while the signal amplitude remains constant.
Microwaves Microwaves are electromagnetic waves with wavelengths ranging from one meter to one millimeter frequencies between MHz and GHz. Learning Objectives Distinguish three ranges of the microwave portion of the electromagnetic spectrum. Key Takeaways Key Points The microwave region of the electromagnetic EM spectrum is generally considered to overlap with the highest frequency shortest wavelength radio waves.
The microwave portion of the electromagnetic spectrum can be subdivided into three ranges listed below from high to low frequencies: extremely high frequency 30 to GHz , super high frequency 3 to 30 GHz , and ultra-high frequency MHz to 3 GHz.
Microwave sources include artificial devices such as circuits, transmission towers, radar, masers, and microwave ovens, as well as natural sources such as the Sun and the Cosmic Microwave Background.
Microwaves can also be produced by atoms and molecules. They are, for example, a component of electromagnetic radiation generated by thermal agitation. Key Terms terahertz radiation : Electromagnetic waves with frequencies around one terahertz. Learning Objectives Distinguish three ranges of the infrared portion of the spectrum, and describe processes of absorption and emission of infrared light by molecules.
Key Takeaways Key Points Infrared light includes most of the thermal radiation emitted by objects near room temperature. This is termed thermography, mainly used in military and industrial applications.
Key Terms emissivity : The energy-emitting propensity of a surface, usually measured at a specific wavelength. Video Transcript all light rays travel at the speed of line that is typically called C. Wave Optics - Intro In physics, wave optics is the study of the behavior of light, or other elec…. Multiple Aperture Interference - Overview Interference is a phenomenon in which two waves superpose to form a resultan….
How fast do X rays travel through a vacuum? What is light? How fast does it travel in a vacuum? Which travels faster through a vacuum: an infrared ray or a gamma ray? The speed at which electromagnetic radiation moves through a vacuum is calle…. At what speed does electromagnetic radiat…. Compare the speed, wavelength, and frequency of radio waves and X-rays trave…. How does the average speed of light in glass compare with its speed in a vac…. How many nanoseconds does it take light to travel 1.
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These waves all travel at the speed of light ,, metres per second in a vacuum. The table below lists the different radiations in the electromagnetic spectrum and shows some information about each radiation.
The electromagnetic spectrum Parts of the electromagnetic spectrum A large family of waves, each with a different wavelength range is called the electromagnetic spectrum sometimes shortened to the EM spectrum.
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