The terminology used to describe different types of electromagnetic radiation can vary and may not always follow a strict pattern. However, historically, the distinction between "rays" and "waves" for X-rays and gamma rays is rooted in the early understanding and discovery of these forms of radiation.
The term "rays" was commonly used in the late 19th and early 20th centuries when X-rays and gamma rays were first discovered and studied. At that time, scientists were investigating the properties of these new forms of radiation and attempting to understand their behavior. The term "rays" was often used to describe the straight-line paths along which these types of radiation appeared to travel.
X-rays were discovered by Wilhelm Conrad Roentgen in 1895, and the name "X-rays" was chosen because the nature of the radiation was unknown at the time. The "X" indicated the unknown or mysterious nature of these rays. Similarly, gamma rays were discovered by Paul Villard in 1900, and the term "gamma" was used to differentiate them from other known forms of radiation, such as alpha and beta particles.
In contrast, the term "waves" is often associated with other forms of electromagnetic radiation because they exhibit wave-like properties, such as wavelength, frequency, and the ability to diffract and interfere. This includes radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, and even certain forms of ionizing radiation, such as ultraviolet and some types of high-energy particle radiation.
It's important to note that both X-rays and gamma rays are forms of high-energy electromagnetic radiation, but they possess properties that distinguish them from other types of radiation. While the terms "rays" and "waves" were initially used to describe these forms of radiation, it's worth emphasizing that all forms of electromagnetic radiation, including X-rays and gamma rays, can be described both as waves and as particles (photons) depending on the context and the phenomena being studied.