According to the electromagnetic spectrum, gamma rays have the shortest wavelength. therefore, gamma rays have frequency.

Gamma rays have highest frequency.

Gamma rays are a type of electromagnetic radiations and these rays are also used for the purpose to treat cancer. When we look at the electromagnetic spectrum, these rays fall above the x-rays. Gamma rays are produces by atomic nuclei.

I believe the answer is: Highest Frequency

frequency refers to  the number of cycles that happened during one unit of time by a body in periodic motion.
Frequenct is calculated with this formula:

f = c / λ

c = wave speed
 λ = wave length

So, as the wavelength got smaller, the frequency would got higher.

One of the European Union's main goals is to promote human rights both internally and around the world. Another is to establish an economic and monetary union whose currency is the euro.