An exposure is made at 200 cm sid and has an intensity of 5 milliroentgens (mr), and a second exposure is made is at 100 cm sid. calculate the intensity of the x-ray beam of the second exposure.

The intensity of X-ray beam of second exposure made at 100 cm SID is 20 mR.

Solution:

By using inverse square law formula, intensity of X-Ray beam made at different distances can be found.

Where is the intensity of first exposure of X-ray-beam.

 is the intensity of second exposure of X-ray beam.

 is the distance at which first exposure is made.  

 is the distance at which second exposure is made.