If the SID doubles while the SOD remains constant, what happens to the magnification factor?

If the SID doubles while the SOD remains constant, what happens to the magnification factor?

• A. It doubles
• B. It halves
• C. It stays the same
• D. It increases by a factor of sqrt(2)

Answer: (C)

Magnification in radiography is determined by the ratio of the source-to-image distance (SID) to the source-to-object distance (SOD). The image size grows in proportion to how much farther the image plane is from the X-ray source compared to the object plane, so the magnification factor is M = SID / SOD. If the SID doubles while SOD stays the same, the ratio SID/SOD doubles as well, so the magnification factor doubles. For example, with SID = 100 cm and SOD = 50 cm, M = 100/50 = 2. If SID becomes 200 cm with the same SOD, M = 200/50 = 4, which is twice the original magnification.

Magnification in radiography is determined by the ratio of the source-to-image distance (SID) to the source-to-object distance (SOD). The image size grows in proportion to how much farther the image plane is from the X-ray source compared to the object plane, so the magnification factor is M = SID / SOD.

If the SID doubles while SOD stays the same, the ratio SID/SOD doubles as well, so the magnification factor doubles. For example, with SID = 100 cm and SOD = 50 cm, M = 100/50 = 2. If SID becomes 200 cm with the same SOD, M = 200/50 = 4, which is twice the original magnification.