Final answer:
True, the angle of the anode target does affect the focal spot size in X-ray tubes; smaller anode angles lead to larger effective focal spot sizes due to geometric projection, although the understanding of numerical aperture (NA) and diffraction in wave optics applies differently.
Step-by-step explanation:
The statement that the angle of the anode target affects the focal spot size is true. In the context of X-ray tubes, the angle of the anode (also known as the target angle) plays a critical role in determining the effective size of the focal spot. The smaller the target angle, the larger the effective focal spot size will be for a given actual focal spot size due to the geometric projection. This is because as the angle decreases, the projected spot size on the anode becomes larger relative to the actual spot size.
It should be noted that while this relationship holds in the domain of radiographic imaging, the provided information from the question refers to the concept of numerical aperture (NA) and diffraction in the context of wave optics, which affects focal spot size differently. Here the NA is about the focusing ability of the lens and diffraction limits which is not directly related to how anode target angle would affect the focal spot size in an X-ray tube.