A gamma ray has a frequency of #2.88 * 10^21# Hz. What does this mean?

1 Answer
Dec 23, 2015

That means it goes through #\mathbf(2.88xx10^(21))# cycles per second. #"1 Hz = 1/s"#.

One cycle is any of the following:

  • from one crest/antinode to the next crest/antinode
  • from one trough to the next trough
  • from one node (zero-crossing) to the next node

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The equation relating frequency to wavelength and speed is:

#color(blue)(upsilon = lambdanu)#

Hence, the speed #upsilon# of a wave is the wavelength #lambda# of the wave multiplied by its frequency #nu#. If we say wavelength is in #"nm"#, then the speed is in #"nm" xx "1/s" = \mathbf("nm/s")#.

The frequency, then, is really just a measure of how fast the wave is propagating forward irrespective of knowing the wavelength.

You can further realize that we have the following equation:

#color(blue)(E = hnu)#

where we should not confuse #upsilon# with #nu#. #upsilon# is speed, while #nu# is frequency (I didn't use #f# because then I would have to redefine #nu = f#).

We can then see that a higher #nu# means a higher energy #E#. The frequency of the gamma ray is very high (it is on the order of #~10^(21)#), so the gamma ray is very strong (high-energy).