How does increasing source-to-object distance affect sharpness?

• A. Decreases beam divergence → sharper image.
• B. Increases beam divergence → blurrier image.
• C. Has no effect on sharpness.
• D. Decreases receptor distance.

Answer: (A)

Sharpness is governed by geometric unsharpness from the X‑ray beam as it travels from the focal spot to the object. Increasing the source-to-object distance makes the beam reach the object more parallel, which reduces the size of the blur (penumbra) projected onto the receptor. That smaller geometric blur yields a crisper image with sharper edges. Keep in mind that a longer distance also lowers beam intensity, so exposure may need adjustment. The other ideas don’t fit because increasing distance does not increase divergence—in fact, it reduces it—and there is a definite effect on sharpness; also, receptor distance mainly affects magnification rather than the inherent sharpness produced by beam divergence.