Frequency:
  • Frequency is the number of complete cycles per second. 
  • The standard unit of frequency is the hertz, abbreviated Hz. 
  • If a current completes one cycle per second, then the frequency is 1 Hz. A previous name for this unit was cycle per second (cps). 
  • Larger units of frequency include the kilohertz (kHz) representing thousands (1,000's) of cycles per second, the megahertz (MHz) representing millions (1,000,000's) of cycles per second, and the gigahertz (GHz) representing billions (1,000,000,000's) of cycles per second. 
     Wavelength:
  • A wavelength is a measure of distance between two identical peaks crests (high points) or troughs (low points) in a wave.
  • It is denoted by λ.
  • Wavelength is measured in meters (m).

      Relation between frequency and wavelength:

  • Wavelength is inversely proportional to frequency. 
  • Waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths, which can be observed in the following figure.
  • Wavelength equation λ = c/f, where c is speed of the wave, f is frequency of the wave.
     Example:
  • The speed of sound is about 340 m/s. Find the wavelength of a sound wave that has a frequency of 20.0 cycles per second.
       Ans: c = 340m/s, f = 20 cycles per second
                 λ = c/f
                 λ = 340/20
                    = 17m