Final answer:
Off-focus and scatter radiation outside of the exposure field in CR contributes to the widening of the histogram, influenced by diffraction, interference, Compton scattering, and spherical aberration.
Step-by-step explanation:
Off-focus and scatter radiation outside of the exposure field when using CR can cause a widening of the histogram due to the diffraction and interference of X-rays. This interference occurs when X-rays, which have been scattered in various directions by the atoms within a crystal or other material, combine and either increase or decrease in amplitude based on the relationship of their wave maxima. Similarly, Compton scattering, where X-rays are scattered off a material and change in wavelength, can also affect the quality of the resulting image. These effects can broaden the intensity distribution, leading to a less sharp central peak.
Additionally, the concept of spherical aberration, where rays striking further from the optical axis are not focused at the same point, also explains how off-focus radiation can distort the image. Chromatic aberration and the relationship of slit width to intensity distribution are other factors that influence the quality of an image captured by a detector, such as a telescope's eyepiece or astronomical observations.