Final answer:
A reduction from 200 to 100 mA leads to a decrease in both beam intensity and exposure rate because of the reduced number of electrons and consequent high-energy photons.
Step-by-step explanation:
A decrease from 200 to 100 mA will result in a decrease in beam intensity. This is because current (measured in milliamperes, mA) is directly proportional to the number of electrons flowing through the circuit per unit time, and a higher current means a higher number of electrons, which contributes to a greater beam intensity. When the current is reduced by half, the rate at which electrons are flowing is also halved, consequently decreasing the beam intensity. Regarding exposure rate, a lower mA will typically result in a longer exposure time to achieve the same amount of radiographic density, therefore, the exposure rate decreases as well when the current decreases.
To answer the question presented: A decrease from 200 to 100 mA in a medical imaging context, for example, would imply that fewer high-energy photons are being produced, resulting in a lower intensity beam and hence lower exposure rate to the patient.