11 Electromagnetic Waves 3 Radio Communication MAINIDEA Write the Main Idea for this lesson. Radio waves and microwaves can be used to transmit signals and information. REVIEW VOCABULARY Recall the definition of the Review Vocabulary term. amplitude amplitude a measure of the size of the disturbance a wave produces NEW VOCABULARY Use your book to define the following key terms. carrier wave carrier wave the specific frequency of the electromagnetic wave that modulation a radio station is assigned analog signal modulation the process of adding the signal wave to the carrier wave digital signal transceiver Global Positioning System analog signal electric signals whose amplitudes change smoothly (GPS) over time digital signal electric signals that have only two values—ON and OFF transceiver a device that transmits one radio signal and receives another Global Positioning System (GPS) a system of satellites, monitoring Copyright © McGraw-Hill Education © McGraw-Hill Copyright stations, and receivers to determine an object’s location near Earth’s surface ACADEMIC VOCABULARY Use a dictionary to define transmit. transmit transmit to send from one location to another Science Notebook • Electromagnetic Waves 177 1167_182_IPC_SN_C11_143655.indd67_182_IPC_SN_C11_143655.indd 177177 007/05/137/05/13 11:44:44 AAMM Program: TX HS Science Component: IPC SCI NTBK PDF PASS Vendor: LASERWORDS Grade: N/A 3 Radio Communication (continued) Student Edition, pp. 352–354 Compare AM and FM radio transmission by completing the organizer Reading Essentials, below. pp. 204–206 Radio Transmission AM radio stations FM radio stations broadcast information by broadcast information by changing the amplitude of changing the frequency the carrier wave. of the carrier wave. GET IT? Compare and contrast AM and FM radio signals. AM radio modulates the amplitude of the carrier wave; FM radio modulates the frequency of the carrier wave. AM waves have lower frequencies than FM waves. GET IT? Describe how a radio signal’s strength changes as you move away from the tower. The radio signal gets weaker as you move away from the tower. Complete the flowchart below to describe the transmission of television signals. Before 2009 TV signals were analog signals, which changed smoothly. Education © McGraw-Hill Copyright Information about color and Information abut sound brightness was sent by was sent on FM waves. AM waves. Beginning in 2009 all TV signals are digital signals. Digital signals are either ON or OFF , like a light switch. Because the switch to digital signals, very complex digital modulation can be carried on a single wave . Science Notebook • Electromagnetic Waves 178 1167_182_IPC_SN_C11_143655.indd67_182_IPC_SN_C11_143655.indd 178178 007/05/137/05/13 11:44:44 AAMM Program: TX HS Science Component: IPC SCI NTBK PDF PASS Vendor: LASERWORDS Grade: N/A 3 Radio Communication (continued) Student Edition, pp. 355–357 Organize what you have learned about telephones by completing the Reading Essentials, table below. pp. 206–208 Type Features Advantage Disadvantage Corded stays in one sends/receives must use in place consistent signal one place Cordless base stays in not linked to the must use near one place base base, can be overheard Pager portable newer ones only responds can send/ to messages receive data with its own ID number Cellular portable not linked to tower needed base Create a sketch to show how a satellite telephone system works. • Use arrows to show the path of the signal. • Include the sender, a satellite, and the receiver in your sketch Sketches should include the sender, with arrows showing the signal moving toward the satellite. Arrows should show the signal moving down toward the receiver. Copyright © McGraw-Hill Education © McGraw-Hill Copyright ANALYZE IT Analyze the information on the Global Positioning System. Infer why the system uses data from four different satellites when locating an object. Accept all reasonable responses. Information from four satellites can locate an exact place. Two receivers give two possible locations. Science Notebook • Electromagnetic Waves 179 1167_182_IPC_SN_C11_143655.indd67_182_IPC_SN_C11_143655.indd 179179 007/05/137/05/13 11:44:44 AAMM Program: TX HS Science Component: IPC SCI NTBK PDF PASS Vendor: LASERWORDS Grade: N/A 3 Radio Communication (continued) REVIEW IT ! 14. MAINIDEA Identify and describe the steps that a radio station uses to broadcast sounds to your radio receiver. Sounds at the radio station are converted into an electrical signal. This signal causes electrons in the broadcast antenna to vibrate. The vibrating electrons produce electromagnetic waves, which travel outward. The electromagnetic wave encounters a radio receiver antenna. The electric and magnetic fields of the wave cause the electrons in the receiver antenna to vibrate. The vibrating electrons provide the electrical signal that the radio converts back into sound. 15. Explain the difference between AM and FM radio. Make a sketch of how a carrier wave is modulated in AM and FM radio signals. Students’ sketches should resemble For AM, amplitude is modulated. For FM, frequency Figure 19. is modulated. 16. Describe what happens to your signal when you are talking on a cell phone and you travel from one cell to another cell. Copyright © McGraw-Hill Education Education © McGraw-Hill Copyright A central controller transfers your signal to the base station in the new cell. 17. Explain some of the uses of the Global Positioning System. Why might emergency vehicles be equipped with GPS receivers? GPS is used by hikers, airplanes, ships, cars, and others to identify their locations on Earth. Emergency vehicles have GPS receivers to help them find places quickly. Science Notebook • Electromagnetic Waves 180 1167_182_IPC_SN_C11_143655.indd67_182_IPC_SN_C11_143655.indd 180180 114/05/134/05/13 112:142:14 AAMM Program: TX HS Science Component: IPC SCI NTBK PDF PASS Vendor: LASERWORDS Grade: N/A 3 Radio Communication (continued) 18. Think Critically Why do cordless telephones stop working when you move too far from the base unit? The strength of the signal decreases with distance, and the signal becomes too weak to be detected by the handset. 19. Calculate a Ratio A TV screen is composed of many points of light called pixels. A standard TV has 460 pixels horizontally and 360 pixels vertically. A high-definition TV has 1,920 horizontal and 1,080 vertical pixels. What is the ratio of the number of pixels in a high-definition TV to the number in a standard TV? (1,920 × 1,080) to (460 × 360) = 2,073,600 to 165,600 = 25 to 2 Copyright © McGraw-Hill Education © McGraw-Hill Copyright Science Notebook • Electromagnetic Waves 181 1167_182_IPC_SN_C11_143655.indd67_182_IPC_SN_C11_143655.indd 181181 007/05/137/05/13 11:44:44 AAMM Program: TX HS Science Component: IPC SCI NTBK PDF PASS Vendor: LASERWORDS Grade: N/A 1167_182_IPC_SN_C11_143655.indd67_182_IPC_SN_C11_143655.indd 182182 007/05/137/05/13 11:44:44 AAMM.