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Frequencies of various radiations are given as fᵥ for visible light, fᵣ for radio waves and fᵤᵥ for ultraviolet waves. Then which of the following is true?

Asked in GUJCET 2018 · Order of the bands

• (1) fᵤᵥ < fᵥ < fᵣ
• (2) fᵣ < fᵥ < fᵤᵥ
• (3) fᵥ < fᵣ < fᵤᵥ
• (4) fᵤᵥ < fᵣ < fᵥ

Step-by-step solution

Why the other options are wrong

• (1) This reverses the order completely, making ultraviolet the lowest and radio the highest. Radio waves have the longest wavelength of the three and so the lowest frequency.
• (3) This puts radio waves above visible light. Radio wavelengths are of the order of metres and visible wavelengths a few hundred nanometres, so fᵣ is the smallest of the three.
• (4) Ultraviolet is placed lowest here, but ultraviolet has the shortest wavelength of the three and therefore the highest frequency.

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