College Physics
1st Edition
ISBN: 9781938168000
Author: Paul Peter Urone, Roger Hinrichs
Publisher: OpenStax College
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Textbook Question
Chapter 24, Problem 34PE
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 modern ones do. This caused identi?able health problems, such as cataracts, for people who worked near them.)
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Suppose the maximum safe average intensity of microwaves for human exposure is taken to be 1.00 W/m2. If a radar unit leaks 10.0 W of microwaves (other than those sent by its antenna) uniformly in all directions, how far away, ?min, must you be to be exposed to an average intensity considered to be safe? Assume that the power spreads uniformly over the area of a sphere with no complications from absorption or reflection.
?min=???
What is the maximum electric field strength ?0 at this distance? The permittivity of free space is ?0=8.854×10−12 C2/(N·m2). The speed of light is ?=3.00×108 m/s.
?0=???
Note: Early radar units leaked more than modern ones do. This caused identifiable health problems, such as cataracts, for people who worked near them.
Assume the mostly infrared radiation from a heat lamp acts like a continuous wave with wavelength 1.50 µm. (a) If the lamp’s 200-W output is focused on a person’s shoulder, over a circular area 25.0 cm in diameter, what is the intensity in W/m2? (b) What is the peak electric field strength? (c) Find the peak magnetic field strength. (d) How long will it take to increase the temperature of the 4.00-kg shoulder by 2.00º C , assuming no other heat transfer and given that its specific heat is 3.47×103 J/kg⋅ºC?
Assume the mostly infrared radiation from a heat lamp acts like a continuous wave with wavelength 1.50 µm . (a) If the lamp’s 200-W output is focused on a person’s shoulder, over a circular area 25.0 cm in diameter, what is the intensity in W/m2 ? (b) What is the peak electric field strength? (c) Find the peak magnetic field strength. (d) How long will it take to increase the temperature of the 4.00-kg shoulder by 2.00º C , assuming no other heat transfer and given that its specific heat is 3.47×103 J/kg ⋅ ºC ?
Chapter 24 Solutions
College Physics
Ch. 24 - The direction of the electric field shown in each...Ch. 24 - Is the direction of the magnetic field shown in...Ch. 24 - Why is the direction of the current shown in each...Ch. 24 - In which situation shown in Figure 24.24 will the...Ch. 24 - In which situation shown in Figure 24.25 will the...Ch. 24 - Should the straight wire antenna of a radio he...Ch. 24 - Under what conditions might wires in a DC circuit...Ch. 24 - Give an example of interference of electromagnetic...Ch. 24 - Figure 24.26 shows the interference pattern of two...Ch. 24 - Can an antenna be any length? Explain your answer.
Ch. 24 - If you live in a region that has a particular TV...Ch. 24 - Explain why people who have the lens of their eye...Ch. 24 - How do ?uorescent soap residues make clothing look...Ch. 24 - Give an example of resonance in the reception of...Ch. 24 - Illustrate that the size of details of an object...Ch. 24 - Why don't buildings block radio waves as...Ch. 24 - Make a list of some everyday objects and decide...Ch. 24 - Your friend says mat more patterns and colors can...Ch. 24 - The rate at which information can be transmitted...Ch. 24 - Give an example of energy carried by an...Ch. 24 - In an MRI scan, a higher magnetic field requires...Ch. 24 - Laser vision correction often uses an excimer...Ch. 24 - Verify that the correct value for the speed of...Ch. 24 - Show that, when SI units for 0 and 0 are entered,...Ch. 24 - What is the maximum electric field strength in an...Ch. 24 - The maximum magnetic field strength of an...Ch. 24 - Verify the units obtained for magnetic field...Ch. 24 - (a) Two microwave frequencies are authorized for...Ch. 24 - (a) Calculate the range of wavelength for AM radio...Ch. 24 - A radio station utilizes frequencies between...Ch. 24 - Find the frequency range of visible light, given...Ch. 24 - Combing your hair leads to excess electrons on the...Ch. 24 - Electromagnetic radiation having a 15.0m...Ch. 24 - Approximately what is the smallest detail...Ch. 24 - A radar used to detect the presence of aircraft...Ch. 24 - Some radar systems detect the size and shape of...Ch. 24 - Determine the amount of time it takes for X-rays...Ch. 24 - If you wish to detect details of the size of atoms...Ch. 24 - If the Sun suddenly turned off, we would not know...Ch. 24 - Distances in space are often quoted in units of...Ch. 24 - A certain 50.0-Hz AC power line radiates an...Ch. 24 - During normal bee?ng, the heat creates a maximum...Ch. 24 - (a) The ideal size (most efficient) for a...Ch. 24 - (a) What is the wavelength of 100MHz radio waves...Ch. 24 - (a) What is the frequency at the 193-nm...Ch. 24 - TV-reception antennas for VHF are constructed with...Ch. 24 - Conversations with astronauts on lunar walks had...Ch. 24 - Lunar astronauts placed a reflector on the Moon's...Ch. 24 - Radar is used to determine distances to various...Ch. 24 - Integrated Concepts (a) Calculate the ratio of the...Ch. 24 - Integrated Concepts (a) Calculate the rate in...Ch. 24 - What is the intensity of an electromagnetic wave...Ch. 24 - Find the intensity of an electromagnetic wave...Ch. 24 - Assume the helium-neon lasers commonly used in...Ch. 24 - An AM radio transmitter broadcasts 50.0 kW of...Ch. 24 - Suppose the maximum safe intensity of microwaves...Ch. 24 - A 2.50-m-diameter university communications...Ch. 24 - Lasers can be constructed that produce an...Ch. 24 - Show that for a continuous sinusoidal...Ch. 24 - Suppose a source of electromagnetic waves radiates...Ch. 24 - Integrated Concepts An LC circuit with a 5.00pF...Ch. 24 - Integrated Concepts What capacitance is needed in...Ch. 24 - Integrated Concepts Police radar determines the...Ch. 24 - Integrated Concepts Assume the mostly infrared...Ch. 24 - Integrated Concepts On its highest power se1ting,...Ch. 24 - Integrated Concepts Electromagnetic radiation from...Ch. 24 - Integrated Concepts A 200-turn flat coil of wire...Ch. 24 - Integrated Concepts If electric and magnetic field...Ch. 24 - Unreasonable Results A researcher measures the...Ch. 24 - Unreasonable Results The peak magnetic field...Ch. 24 - Unreasonable Results An LC circuit containing a...Ch. 24 - Unreasonable Results An LC circuit containing a...Ch. 24 - Create Your Own Problem Consider electromagnetic...Ch. 24 - Create Your Own Problem Consider the most recent...
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