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A wave has a frequency of 6 × 10¹⁵ Hz. This wave belongs to the category of

1. radio wave
2. microwave
3. X-ray
4. none of these

Correct answer: none of these

Solution

lambda = c/f = 3e8/6e15 = 5e-8 m = 50 nm, which lies in the (extreme) ultraviolet band. X-rays have wavelengths below ~10 nm (f > ~3e16 Hz). Since UV is not listed, the answer is 'none of these'.

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