OBSERVATION. ‘One peak is located at the wavelength  which is the wavelength of the incident beam. The other peak is located at some other wavelength,  The two peaks are separated by  which depends on the scattering angle  of the outgoing beam (in the direction of observation). The separation  is called the Compton shift.”
https://opentextbc.ca/universityphysicsv3openstax/chapter/the-compton-effect/#:~:text=The%20Compton%20effect%20is%20the,wavelength%20of%20the%20incident%20radiation
