Answer:
Electric and magnetic fields at right angles to each other.
Step-by-step explanation:
Gamma rays like any other electromagnetic waves are simply produced when electric and magnetic fields are oriented at right angles to each other.
These waves produced in this unique way are called electromagnetic waves.
Electromagnetic waves do not require a material medium for their propagation in nature as they move in vacuum and other forms of matter.
Other examples of these waves are x-rays, visible light, infra-red, ultraviolet e.t.c
All of these are produced when electric and magnetic fields are oriented at right angles to one another.