ANS:C - The quality of X-rays can be controlled by varying the anode-cathode voltage.

The quality of X-rays refers to their energy or wavelength distribution, which can be controlled by adjusting the voltage applied between the anode and cathode in an X-ray tube. This phenomenon is known as the "tube voltage" or "kilovoltage peak" (kVp). When electrons are accelerated from the cathode to the anode in an X-ray tube, they strike the target (anode) with kinetic energy. This energy is converted into X-rays when the electrons interact with the target material, typically a metal such as tungsten. The energy of the resulting X-rays depends on the voltage applied across the X-ray tube. By increasing or decreasing the tube voltage (kVp), the energy of the electrons and consequently the energy of the X-rays emitted can be controlled. Higher voltages result in electrons with greater kinetic energy, leading to the production of X-rays with higher energy levels (shorter wavelengths). Lower voltages produce X-rays with lower energy levels (longer wavelengths). Controlling the quality of X-rays is important in various applications such as medical imaging, where different tissues absorb X-rays differently depending on their energy levels. Adjusting the voltage allows for optimizing the X-ray beam to penetrate specific materials or tissues and produce clearer images with improved contrast.