1103 Period 26: Broadcasting

Transcription

1 Name Section 1103 Period 26: Broadcasting Activity 26.1: Broadcasting Information with Radiant Energy 1) Transferring information with electromagnetic radiation: a) What is a carrier wave? 2) Radio wave transmissions: Your instructor will discuss broadcasting. a) How is it possible that every radio station transmits its signal at a distinct frequency while sending a signal made up of a variety of frequencies (musical pitches)? b) A radio station transmits radio waves with a carrier wavelength of 3.3 meters. What is the frequency of the station? Activity 26.2: Methods of Transferring Signals 3) How are signals transmitted? a) List 3 common mediums through which an electromagnetic signal can be transmitted. b) How does a fiber optic cable transmit information? How is it possible for a signal to be transmitted through a bent cable? c) How do coaxial cables transmit information? d) Group Discussion Question: Fiber optic cables can carry information at higher frequencies than coaxial cables can. What advantage do higher frequencies provide for information transfer? 163

2 Activity 26.3: Methods of Modulating Signals 4) Amplitude and frequency modulation: Your instructor will discuss AM and FM. a) How can modulation of wave amplitude broadcast information? b) How can modulation of wave frequency braodcast information? c) Which type of modulation is less likely to be affected by noise in a radio broadcast? Activity 26.4: Digital Information Transfer 5) Digital transmissions: a) How does a digital broadcast differ from an analog AM or FM broadcast? b) What is a pixel? Look for pixels in the pictures on your table. c) Using Morse code and telegraph keys, have a contest between two groups at your table. Try to send and successfully receive your mother s first name. Is Morse code an analog or a digital signal? Why? d) Have one person at your table speak softly (the sender of the signal) to another person sitting across the table (the receiver), while the rest of those at the table talk loudly (the noise). Can the receiver understand the signal? Repeat the experiment with the signal sender softly speaking the words one or zero while the others talk loudly. In which case is it easier for the receiver to understand the signal? e) Look at the photographs with the noise filter in front of them. Could you determine which picture was which? Now look at the numbers representing each picture. Can you distinguish the numbers when they are obscured by the filter? f) Group Discussion Question: Why is digitally encoding information an improvement over analog information? 164

3 Name Section Optional Activity 26.5: Communicating with Polarized Radiant Energy 6) Polarized Radiant Energy: Your instructor will discuss polarization of light. a) Look at the classroom ceiling lights through a polarizing filter. What happens to the light from the ceiling bulbs when it passes through the filter? b) Look at the ceiling lights through two polarizing filters. What happens when you rotate one of the filters? c) Light reflected from a horizontal surface, such as a mirror, becomes polarized. Look at the OHIO sign and the reflection of the sign. Now view the sign and its reflection through a polarizing filter. Describe what happens when you rotate the polarizing filter. Why does rotating the filter have this effect? 7) Microwave transmissions a) Microwave transmissions are usually sent between a source and a single receiver. Use a microwave transmitter to send microwaves to the microwave receiver. Try to shield the signal using a sheet of aluminum, a glass plate, and a metal grid. Try to reflect the microwave signal using the same materials. Record your results below. Shields waves? Reflects waves? Aluminum sheet Glass plate Grid held horizontally Grid held vertically b) Why do different orientations of the metal grid give different results? c) Group Discussion Question: Why does a microwave oven have a glass door with metal gratings? 165

4 8) Three-D glasses and information transfer a) Look at the classroom ceiling lights through one lens of 3-D glasses. Hold a polarizing filter between the glasses lens and the ceiling light. Rotate the filter. Describe what you see. b) Repeat the experiment as you look through both lens of the 3-D glasses at the same time. Describe what you see. What must be true of the lenses in the 3-D glasses to cause the effect you observe? c) A video shown in 3-D uses two projectors that send different images to the screen. The two images are projected through polarizing filters and are superimposed on the movie screen. Explain how 3-D glasses could let each of your eyes view only one of the images on the screen. d) To show the effect of binocular vision when each eye sees a different image, hold one raised finger in front of your face. Look at your finger with one eye closed, then open that eye and close the other eye. Describe what happens. How could this produce the image of objects on a movie screen appearing to move toward you? 166

5 1103 Period 26 Exercises: Today s Technology This sheet with your answers should be turned in by the time of the final exam. One goal of Physics 1103 is to provide information relating to the technology we use today. Explain how physics concepts we have studied this semester relate to each of the devices or technologies listed below. Use ideas from your class activities, the assigned videos and your own opinions to answer the questions. How does technology affect your life? 1) Computers: 2) The internet and the World Wide Web: 3) Iphones, ipads, and other wireless communication devices: 167

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