The highest frequency rays in the electromagnetic spectrum are gamma rays. They have the highest energy and the shortest wavelength, with frequencies ranging from about 10¹⁹ Hz to 10²⁵ Hz.

Here's a breakdown of the electromagnetic spectrum from lowest to highest frequency:

1. Radio waves (lowest frequency)

2. Microwaves

3. Infrared radiation

4. Visible light

5. Ultraviolet radiation

6. X-rays

7. Gamma rays (highest frequency)

Remember that frequency and energy are directly proportional. So, the higher the frequency, the higher the energy of the radiation. Gamma rays are the most energetic form of electromagnetic radiation, and they can be incredibly harmful to living organisms.