The ratio of velocity of X-rays to that of gamma rays

X-rays and gamma rays are both forms of electromagnetic radiation [t1]. All electromagnetic waves, regardless of their frequency or wavelength, travel at the same constant speed in a vacuum, which is approximately 3 × 10^8 m/s, commonly denoted as 'c' [t4]. While X-rays and gamma rays differ significantly in their origin, photon energy, and frequency—with gamma rays being more energetic and having higher frequencies—their fundamental nature as electromagnetic waves ensures they propagate at the same velocity in a vacuum [t1][t6]. Specifically, the speed of X-rays in a vacuum is identical to that of visible light and gamma rays [t2][t5]. Therefore, the ratio of the velocity of X-rays to that of gamma rays is exactly 1, as both values are equal to the speed of light [t3][t9].

Sources

1. [1] https://imagine.gsfc.nasa.gov/science/toolbox/emspectrum1.html