In radiographic geometry, increasing the object-to-image distance (OID) will:

In radiographic geometry, increasing the object-to-image distance (OID) will:

• A. Decrease magnification
• B. Increase magnification
• C. Have no effect on magnification
• D. Increase SID

Answer: (B)

Magnification in radiography comes from the geometry of X-ray projection. The image size depends on the distance from the source to the detector (SID) and the distance from the source to the object (SOD). The magnification factor is M = SID / SOD. If you increase the object-to-image distance while keeping SID fixed, the SOD must decrease (since SID = SOD + OID). A smaller SOD with the same SID makes the ratio SID/SOD larger, so the image will be larger than the object. In practical terms, the farther the object is from the image receptor, the more the beam diverges before it hits the receptor, producing greater magnification. Hence, increasing OID increases magnification.

Magnification in radiography comes from the geometry of X-ray projection. The image size depends on the distance from the source to the detector (SID) and the distance from the source to the object (SOD). The magnification factor is M = SID / SOD. If you increase the object-to-image distance while keeping SID fixed, the SOD must decrease (since SID = SOD + OID). A smaller SOD with the same SID makes the ratio SID/SOD larger, so the image will be larger than the object. In practical terms, the farther the object is from the image receptor, the more the beam diverges before it hits the receptor, producing greater magnification. Hence, increasing OID increases magnification.