Question
Determine the amount of time it takes for X-rays of frequency 3×1018 Hz3 \times 10^{18} \textrm{ Hz} to travel (a) 1 mm and (b) 1 cm.
Question by OpenStax is licensed under CC BY 4.0
Final Answer
  1. 3×10−12 s3 \times 10^{-12} \textrm{ s}
  2. 3×10−11 s3 \times 10^{-11} \textrm{ s}

Solution video

OpenStax College Physics for AP® Courses, Chapter 24, Problem 15 (Problems & Exercises)

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Video Transcript
This is College Physics Answers with Shaun Dychko. This question asks us to find the amount of time it takes for some x-rays to travel one millimeter or one centimeter and it gives us the frequency as well; 3 times 10 to the 18 Hertz, But it turns out this frequency is irrelevant because the time will just be the distance that the wave has to travel divided by the speed at which it travels and all the wavelengths will travel at the same speed of light. And so the time will be 1 times 10 to the minus 3 meters divided by 3 times 10 to the 8 meters per second, which is 3 times 10 to the minus 12 seconds, or to travel one centimeter, it will be 1 times 10 to the minus 2 meters divided by the speed of light which is 3 times 10 to the minus 11 seconds.