Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: The Speed of Light

  1. Mar 21, 2006 #1
    I was having a little trouble understanding a concept in my book. My book asked the following question:

    The frequency of electromagnetic wave A is twice that of electromagnetic wave B. For these two waves, which is the ratio wavelengthA/wavelengthB of the wavelengths in a a vacuum?

    The answer turned out to be that the ratio would equal 1/2 because both waves have the same speed. I was able to calculate the 1/2 in my ratio, but I didn't understand how both waves would have the same velocity. I know frequency * wavelenth = velocity. If frequency is twice as large in one wave, how can they have the same speed?
  2. jcsd
  3. Mar 21, 2006 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Frequency * wavelength = velocity.

    If velocity is fixed, then doubling frequency requires halving wavelength. That's what the question wanted you to realize.

    - Warren
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook