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The specific absorption rate (SAR) is the amount of RF energy from the phone absorbed by the user’s body. Different cell phones have different SAR levels. Different phones give off different amounts of energy.Ĭell phone specific absorption rate (SAR) Higher traffic (from many people using cell phones) may require more energy to get a good signal. The amount of cell phone traffic in the area at the time.Being farther away from the tower requires more energy to get a good signal, as does being inside a building. Cell phones adjust their power to use the minimum amount for a good signal. The distance and path to the nearest cell phone tower.The farther away from a person's body the phone is, the less they are exposed. Whether the person is holding the phone close to the head, or is instead using the speaker mode or a hands-free device.The amount of time the person is on the phone.Many factors can affect the amount of energy from RF waves that a person is exposed to, including: The body tissues closest to the phone absorb more energy from RF waves than tissues farther away. The closer the antenna is to a user's head, the greater their expected exposure to RF waves. The phone is often held against the head when a person is on a call. The waves are strongest at the antenna and lose energy quickly as they travel away from the phone. The RF waves come from the cell phone's antenna, which is part of the body of a hand-held phone. But the levels of energy given off by cell phones are much lower, and are not enough to raise temperatures in the body. The electromagnetic spectrum illustration shows the possible frequencies of electromagnetic energy, ranging from extremely low frequencies (such as those from power lines) to exposures from extremely high frequencies (x-rays and gamma rays), and includes both non-ionizing and ionizing radiation.Īt very high levels, RF waves can heat up body tissues. Ionizing radiation can break the chemical bonds in DNA, which might lead to cancer. RF waves are different from stronger ( ionizing) types of radiation such as x-rays, gamma rays, and ultraviolet (UV) rays.
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They don’t have enough energy to cause cancer by directly damaging the DNA (genes) inside cells. Like FM radio waves, microwaves, visible light, and heat, RF waves are a form of non-ionizing radiation. This is a form of energy in the electromagnetic spectrum that falls between FM radio waves and microwaves. How do cell phones work?Ĭell phones send signals to (and receive them from) nearby cell towers (base stations) using RF waves. The main concerns have focused on whether cell phones might increase the risk of brain tumors or other tumors in the head and neck area, as these areas are closest to where the phone is usually held while talking or listening on a call. Since then, along with the large and still growing number of cell phone users (both adults and children), the amount of time people spend on their phones has also risen sharply.Ĭell phones give off a form of energy known as radiofrequency (RF) waves, so the safety of cell phone use has raised some concerns. 6.Cellular (cell or mobile) phones first became widely available in the United States in the 1990s. to achieve a well-defined small area in which the X-rays are created. refracting X-rays In an X-ray tube, the anode cone has a bevel a. In the x-ray tube, the evacuated vessel is surrounded by oil for a. The anode material used in x-ray tubes should have a a. Electrons from cathode striking an inner-shell electron of the anode's atom. Deflection of electrons coming from the cathode when passing close to an atomic nucleus of anode losing some of their kinetic energy. Excitation and ionization of the anode atoms by electrons b. Characteristic x-rays are produced as a result of a. Electrons from cathode strike an inner-shell electron of the anode's atom. Electrons from cathode deflect when passing close to an atomic nucleus of anode losing some of their kinetic energy c. Excitation and ionization of the anode atoms by accelerated electrons take place b. Bremsstrahlung x-rays are the wide range of x-ray produced as when: a. It's refractive indices are approximately the same for different materials c. It does not propagate like electromagnetic radiation b. X-rays cannot be focused by means of lenses because: a.