The Specific Absorption Rate (SAR) for a cell phone measures the amount of radio frequency (RF) energy absorbed by the user’s body when using the handset. Every cell phone emits RF energy. Different phone models have different SAR measures. To receive certification from the Federal Communications Commission (FCC) for sale in the United States, the SAR level for a cell phone must be no more than 1.6 watts per kilogram. Table 8.1 shows the highest SAR level for a random selection of cell phone models as measured by the FCC. Phone Model SAR Phone Model SAR Phone Model SAR Apple iPhone 4S 1.11 LG Ally 1.36 Pantech Laser 0.74 BlackBerry Pearl 8120 1.48 LG AX275 1.34 Samsung Character 0.5 BlackBerry Tour 9630 1.43 LG Cosmos 1.18 Samsung Epic 4G Touch 0.4 Cricket TXTM8 1.3 LG CU515 1.3 Samsung M240 0.867 HP/Palm Centro 1.09 LG Trax CU575 1.26 Samsung Messager III SCH-R750 0.68 HTC One V 0.455 Motorola Q9h 1.29 Samsung Nexus S 0.51 HTC Touch Pro 2 1.41 Motorola Razr2 V8 0.36 Samsung SGH-A227 1.13 Huawei M835 Ideos 0.82 Motorola Razr2 V9 0.52 SGH-a107 GoPhone 0.3 Kyocera DuraPlus 0.78 Motorola V195s 1.6 Sony W350a 1.48 Kyocera K127 Marbl 1.25 Nokia 1680 1.39 T-Mobile Concord 1.38 Table 8.1 Problem Find a 98% confidence interval for the true (population) mean of the Specific Absorption Rates (SARs) for cell phones. Assume that the population standard deviation is σ = 0.337.
Added by John D.
Step 1
Since we are trying to estimate a population mean, we choose the sample mean (x̄) as the sample statistic. Show more…
Show all steps
Close
Your feedback will help us improve your experience
Lucas Finney and 67 other Intro Stats / AP Statistics educators are ready to help you.
Ask a new question
Labs
Want to see this concept in action?
Explore this concept interactively to see how it behaves as you change inputs.
Key Concepts
Recommended Videos
The frequency and wavelength of EM waves can vary over a wide range of values. Scientists refer to the full range of frequencies that EM radiation can have as the electromagnetic spectrum. Electromagnetic waves are used extensively in modern technology. Many devices are built to emit and/or receive EM waves at a very specific frequency, or within a narrow band of frequencies. Here are some examples followed by their frequencies of operation: garage door openers: 40.0 MHz standard cordless phones: 40.0 to 50.0 MHz baby monitors: 49.0 MHz FM radio stations: 88.0 to 108 MHz cell phones: 800 to 900 MHz Global Positioning System: 1227 to 1575 MHz microwave ovens: 2450 MHz wireless internet technology: 2.4 to 2.6 GHz Which of the following statements correctly describe the various applications listed above? Check all that apply. a.) All these technologies use radio waves, including low-frequency microwaves. b.) All these technologies use radio waves, including high-frequency microwaves. c.) All these technologies use a combination of infrared waves and high-frequency microwaves. d.) Microwave ovens emit in the same frequency band as some wireless Internet devices. e.) The radiation emitted by wireless Internet devices has the shortest wavelength of all the technologies listed above. f.) All these technologies emit waves with a wavelength in the range of 0.10 to 10.0 m. g.) All the technologies emit waves with a wavelength in the range of 0.01 to 10.0 km.
Madhur L.
Depending on the situation, a cell phone will project between 0.02 W and 2 W of radiowave radiation. While using your phone, you measure the output and find that your phone is producing radiowaves at a rate of 0.84 Watts. At a distance of 2 cm, what is the average intensity of these waves? 0.396 W/m^2 Remember that the intensity I of an electromagnetic field is: I = cε0E^2 = cB^2/μ0 where c is the speed of light and E and B are the magnitudes of the electric and magnetic field, respectively. The constant ε0 is the permeability of free space and μ0 is the permeability of free space constant. Please remember that we are solving for the peak intensity of the wave using the peak magnitude of the electric field. The next step is slightly different. What is the peak intensity of the wave at this distance? 5.94 W/m^2 Remember that the average intensity Iav of an electromagnetic field is: Iav = cε0Erms^2 = cBrms^2/μ0 The constant ε0 is the permeability of free space and μ0 is the permeability of free space constant. The speed of light is c and Erms = (1/2)^1/2Emax and Brms = (1/2)^1/2Bmax are the rms magnitudes of the electric and magnetic field, respectively. Please remember to now solve for the average intensity of the wave using the peak magnitude of the electric field. Calculate the peak electric field strength E0 in these waves. N/C Calculate the peak magnetic field strength B0 in these waves. T
Timothy J.
Two radio waves are used in the operation of a cellular telephone. To receive a call, the phone detects the wave emitted at one frequency by the transmitter station or base unit. To send your message to the base unit, your phone emits its own wave at a different frequency. The difference between these two frequencies is fixed for all channels of cell phone operation. Suppose the wavelength of the wave emitted by the base unit is 0.34647 m and the wavelength of the wave emitted by the phone is 0.36270 m. Using a value of 2.9979 × 108 m/s for the speed of light, determine the difference between the two frequencies used in the operation of a cell phone. Give your answer to four significant figures.
Adi S.
Recommended Textbooks
Elementary Statistics a Step by Step Approach
The Practice of Statistics for AP
Introductory Statistics
Transcript
Watch the video solution with this free unlock.
EMAIL
PASSWORD