Final answer:
The energy or quality of the X-rays produced is directly controlled by the voltage. Higher voltage leads to X-rays with higher energy, shorter wavelength, and greater ability to penetrate matter. Therefore, the correct answer is 1) Voltage.
Step-by-step explanation:
The energy or quality of the X-rays produced is directly controlled by the voltage of the X-ray tube. When the tube voltage is increased, the electrons are accelerated to greater speeds and, upon striking the target material, can generate X-rays with higher energy.
Therefore, the higher the voltage, the higher the energy of the X-rays produced. This is due to the fact that the photon energy (E) of the X-rays is proportional to the frequency (f), following E=hf, where h is Planck's constant, and frequency is related to the accelerating voltage.
A higher voltage means more energy is transferred to the electrons, which then emit X-rays with higher frequency and, consequently, shorter wavelength, upon collision with the target material.
Current, on the other hand, controls the quantity of X-rays produced, as it determines the number of electrons available to produce X-rays. Frequency and wavelength are properties of the X-rays themselves, where frequency is inversely proportional to wavelength (λ), following the relationship c = fλ, where c is the speed of light.
To put it more succinctly, as voltage increases, the shortest possible wavelength of the X-rays decreases, which means their energy, as measured in electron volts (eV), increases.