Two Radio Antennas Are $10 \mathrm {~km}$ Apart on a North-South Axis on High Mountain Tops at North-South

question 136

Multiple Choice

Two radio antennas are $10 \mathrm {~km}$ apart on a north-south axis on high mountain tops at the seacoast. The antennas broadcast identical AM radio signals, in phase, at a frequency of $4.70 \mathrm { MHz }$ . A steamship, $200 \mathrm {~km}$ offshore, travels toward the north at $15 \mathrm {~km} / \mathrm { h }$ and passes east of the antennas. A radio on board the ship is tuned to the broadcast frequency. The reception of the radio signal on the ship is a maximum at a given instant. How much later until the next occurrence of maximum reception? $\left( c = 3.00 \times 10 ^ { 8 } \mathrm {~m} / \mathrm { s } \right)$

• A) \(6.4 \mathrm {~min}\)
• B) \(7.7 \mathrm {~min}\)
• C) \(3.8 \mathrm {~min}\)
• D) \(8.9 \mathrm {~min}\)
• E) \(5.1 \mathrm {~min}\)

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