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nagle_phys2020_fa07_lecture33 - CAPA#12 due this Friday...

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1 19 • CAPA #12 due this Friday • Details of Exam #3 covered on Wednesday this week • Office hours today moved to 3:30-4:30 pm Re-Try: Transmitter + Antenna Receiver 20 Visible Light: λ = 400 nm (violet) Æ 700 nm (red) Example: λ = 500 nm (yellow) f = c/ λ = 3x10 8 /550x10 -9 = 5x10 14 Hz 21 Television transmissions are in the “radio” range. λ = 1-5 meters f ~ 10 8 Hz = 100 MHz On Television, different channels have different frequencies and thus different wavelengths. When you set the channel knob, you amplify just that frequency range. 22 23 Signal (picture information) is carried by a range of frequencies ( Δ f = “bandwidth”) centered on a “carrier frequency” f. Information is encoded either by: Amplitude Modulation (AM) Frequency Modulation (FM) Under cover of night, a Girl scout signals her friends on a distant hill by alternately placing slabs of red or green Jell-O over her flashlight. This signal is most accurately described as.. A: Amplitude modulation. B: Frequency modulation. AM FM dim bright less bright Answer: When the Girl scout signals by changing the color of the light (keeping
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