The Radiation Theory states that when a ghost/spirit manifests in an area that the ghost/spirit will give off some kind of radiation, such as Gamma, Beta, Microwave, and/or Ultra Violet (UV).
Gamma Radiation: Can pass through most solid objects due to its extremely short wavelength. Two sources of gamma radiation are cosmic activity and radioactive materials.
Beta Radiation: Radioactive nuclei that sends out high-energy electrons with a negative charge. This radiation can pass though wooden walls and clothing.
Microwave Radiation: An extremely high frequency of electromagnetic waves and radio waves.
Ultra Violet (UV) Radiation: Wavelengths of Electromagnetic radiation shorter than visible light.
Some of the meters that we use to detect Radiation are listed below:
Gamma Radiation Beta Radiation
Microwave Radiation Ultra Violet (UV) Radiation