Introduction To Health Physics
5th Edition
ISBN: 9780071835275
Author: Johnson, Thomas E. (thomas Edward), Cember, Herman.
Publisher: Mcgraw-hill Education,
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Question
Chapter 14, Problem 14.23P
To determine
The attenuation in decibels that would reduce a field of 800 mW/cm2to the power density of 1 mW/cm2recommended by ICNIRP for occupational exposure to 300-GHz
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AM radio waves can be produced by a marconi anthenna, whose length must be one-fourth of the wave's wavelength. What must be the length, in meters, of the antenna to produce a frquency of 630kHz?
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The ICNIRP also has guidelines for magnetic-field exposure for the general public. In the frequency range of 25 Hz to 3 kHz, this guideline states that the maximum allowed magnetic-field amplitude is 5>f T, where f is the frequency in kHz. Which is a more stringent limit on allowable electromagnetic-wave intensity in this frequency range: the electric-field guideline or the magnetic-field guideline? (a) The magnetic-field guideline, because at a given frequency the allowed magnetic field is smaller than the allowed electric field. (b) The electric-field guideline, because at a given frequency the allowed intensity calculated from the electric-field guideline is smaller. (c) It depends on the particular frequency chosen (both guidelines are frequency dependent). (d) Neither—for any given frequency, the guidelines represent the same electromagneticwave intensity
Chapter 14 Solutions
Introduction To Health Physics
Ch. 14 - Prob. 14.11PCh. 14 - Calculate the gain of a 30-cm-diameter parabolic...Ch. 14 - Prob. 14.13PCh. 14 - Prob. 14.14PCh. 14 - What is the maximum magnetic intensity in a plane...Ch. 14 - Prob. 14.16PCh. 14 - A rectangular horn antenna, 17cm24cm and operating...Ch. 14 - Prob. 14.18PCh. 14 - Prob. 14.19PCh. 14 - Prob. 14.20P
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- Suppose the maximum safe intensity of microwaves for human exposure is taken to be 1,00 W/m2. (a) If a radar unit leaks 10.0 W of microwaves (other than those sent by its antenna) uniformly in all directions, how far away must you be to be exposed to an intensity considered to be safe? Assume that the power spreads uniformly over the area of a sphere with no complications from absorption or reflection, (b) What is the maximum electric field strength at the safe intensity? (Note that early radar units leaked more than modem ones do. This caused identifiable health problems, such as cataracts, for people who worked near them.)arrow_forwardAn AM radio transmitter broadcasts 54.0 kW of power uniformly in all directions. (a) Assuming all of the radio waves that strike the ground are completely absorbed, and that there is no absorption by the atmosphere or other objects, what is the intensity (in W/m2) 26.0 km away? (Hint: Half the power will be spread over the area of a hemisphere.) W/m2 (b) What is the maximum electric field strength (in V/m) at this distance? V/marrow_forwardAn AM radio transmitter broadcasts 45 kW of power uniformly in all directions.Randomized VariablesP = 45 kWd = 29 km Part (a) Assuming all of the radio waves that strike the ground are completely absorbed, and that there is no absorption by the atmosphere or other objects, what is the intensity 29 km away? Part (b) What is the maximum electric field strength at this distance, in N/C?arrow_forward
- A uniform plane wave in free space is given by: Exs=800cos(10^8t - βz)az V/m Find: Phase constant, propagation speed, wavelength and intrinsic impedance. Magnetic field intensity at the point (0.1,1.5,0.4), t = 8ns Power density for the same point.arrow_forwardAssume the helium-neon lasers commonly used in student physics laboratories have power outputs of 0.250 mW. (a) If such a laser beam is proje ted onto a circular spot 3.50 mm in diameter, what is its intensity (in watts per meter squared)? W/m² (b) Find the peak magnetic field strength (in teslas). T (c) Find the peak electric field strength (in volts per meter). V/marrow_forwardGiven the magnetic flied intensity in vacuum H = 2.23 ax + 3.25 ay + 2.00 az milliamperes per meter. Determine the amount of flux, in webers, passing through the rectangular plane of dimensions 3.77 cm by 3.98 cm lying on y = 1.01 meters in the +y-direction. Use u0 = 4pi x 10e-7 H/m.arrow_forward
- Radio receivers can comfortably pick up a broadcasting station's signal when the electric field strength of the signal is about 10.0 mV/mmV/m. If a radio station broadcasts in all directions with an average power of 54.0 kWkW, what would be the maximum distance at which you could easily pick up its transmissions? (Atmospheric conditions can have major effects on this distance.) Express your answer with the appropriate units.arrow_forwardCalculate the peak electric and magnetic fields 32.1 km from a 1.0MW radio station, assuming that it radiates electromagnetic waves as an isotropic point source.arrow_forwardDuring the Cold War, American submarines operated as "lone wolves" at extreme ocean depths for many months at a time. Ordinary radio signals are greatly attenuated at such depths, making communication with the submarines difficult. One way suggested to communicate with the submarines was a program the Navy called Seafarer that used extremely low frequency waves. If the Seafarer transmitter broadcast at 82 Hz, what would the transmitter's quarter wavelength antenna have to be in order to receive the signal? kmarrow_forward
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