The speed of light is called c for ease of use . The shorter the wavelength the greater the penetration.
Radioactive decay is spontaneous.
This can occur when a neutron splits into an electron and a proton. K-capture is the capture of the inner most electron, combined with one of the nucleus' protons, to make a neutron. In both cases, the new products are of a slightly mass than the originals. On Earth gamma rays originate largely from cosmic radiation. Bubble chambers use a pressurized tank of H 2 .