The speed of all electromagnetic waves in a vacuum is

  • A. 3 times 10 to the 8 m per second, whatever their frequency
  • B. different for each frequency
  • C. 340 m per second
  • D. dependent on the intensity

Explanation

In a vacuum every electromagnetic wave from radio to gamma travels at the same speed c, so wavelength and frequency vary inversely. In a material medium the speed falls and does depend slightly on frequency, which is the dispersion that splits white light in a prism. The value 340 m per second is the speed of sound in air.

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