If SID is halved, what may be said about receptor exposure?

If SID is halved, what may be said about receptor exposure?

• A. Receptor exposure doubles
• B. Receptor exposure is reduced by half
• C. Receptor exposure is reduced by one-half of the mAs
• D. Receptor exposure is quadrupled

Answer: (D)

Exposure at the receptor follows the inverse square law: receptor exposure is proportional to the mAs divided by the square of the distance (SID). If you halve the SID and keep the same mAs, the exposure increases by a factor of four because the distance term in the denominator becomes (1/2)^2, which is 1/4, making the overall exposure four times greater. So receptor exposure is quadrupled when SID is halved and mAs is unchanged. To maintain the same exposure with a shorter distance, you would reduce the mAs to one-quarter of its original value. The other options don’t fit this distance-based fourfold increase.

Exposure at the receptor follows the inverse square law: receptor exposure is proportional to the mAs divided by the square of the distance (SID). If you halve the SID and keep the same mAs, the exposure increases by a factor of four because the distance term in the denominator becomes (1/2)^2, which is 1/4, making the overall exposure four times greater. So receptor exposure is quadrupled when SID is halved and mAs is unchanged. To maintain the same exposure with a shorter distance, you would reduce the mAs to one-quarter of its original value. The other options don’t fit this distance-based fourfold increase.