infrared frequency twice that of radio waves

casualsettheory

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Sep 14, 2019
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hi! i have a quick question, a pretty logical one though... please enlighten me, am I really that exhausted or is the sentence "the frequency of infrared radiation (which has a wavelength of 1.0 * 10^3 nm) is twice that of radio waves (which has a wavelength of 1.0 * 10^6 nm)" incorrect? I mean, the logic is pretty simple, frequency equals the speed of light over wavelength, so frequency is directly proportional with 1/wavelength, so the ratio should be 10^3. But isn't twice supposed to be two times something? Wasn't the ratio supposed to be two then? Am I missing something? Thanks!
 
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Dr.Peterson

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You're right that the statement is wrong. The ratio of those two wavelengths is 1:10^3, so the ratio of the frequencies (which are inversely proportional to wavelength) is 10^3:1, not 2:1.

Who said it?
 

casualsettheory

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Sep 14, 2019
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Thank you very much for your confirmation! The statement is from one of my college chemistry textbooks. One of the exercises requires to state which of the following claims is true, but all four of them are wrong, from my perspective. The first one is the one that I had mentioned, the second one is worded exactly like this only changed "twice" with "a half" (probably to test if we know that frequency and wavelength are not directly proportional), third says that "x-rays travel faster than infrared radiation because they have higher energy" but all types of radiation travel at the same speed (of light) in vacuum, and the last one says that "the wavelength of visible radiation decreases as its color changes from blue to green", but in fact, it increases, and the frequency decreases. Perhaps all statements are meant to be wrong and it is a trick question, or, in the worst case possible, what they meant by "twice the frequency of radio waves" is "twice the exponent", not the actual number... Nevertheless, thank you very deeply for answering my question!
 
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