One of the "Quiet" Bands in the Electromagnetic Spectrum Used

question 16

Multiple Choice

One of the "quiet" bands in the electromagnetic spectrum used for SETI is the so-called "water hole" between about 10³ and 10⁴ MHz. What is the principal source of the natural signals in this frequency band?

• A) emissions from the water molecule
• B) emissions from oxygen molecules
• C) cosmic microwave background radiation
• D) radio emission from terrestrial sources

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