Which of the following is NOT a true statement about the three variable factors kVp, mA, and time?

• A. They include distance and angle of the tubehead
• B. They are the three variable factors to set on the x-ray machine
• C. They are all related to image quality and exposure
• D. They determine exposure characteristics

Answer: (A)

The main idea here is understanding what controls exposure on a dental x-ray unit. The three adjustable factors—kVp, mA, and exposure time—directly set how much radiation reaches the image receptor and how that radiation behaves. They determine the beam’s energy, quantity, and ultimately the density and contrast of the image. Distance and angle of the tubehead are separate geometric factors that influence exposure and image sharpness through beam alignment, magnification, and the inverse square law, but they are not part of the three exposure factors you adjust on the machine.

So the statement that distance and angle are included among the three variable factors is not true. The other statements are correct: these three values are the variables you set on the x-ray machine, they relate to image quality and exposure, and they determine exposure characteristics.