Frequency of X-rays depends upon:

Explanation

The frequency of X-rays depends on the accelerating potential (voltage) applied to the X-ray tube. This is because the energy of the X-rays is related to the voltage, and energy is directly proportional to frequency (E = hf, where E is energy, h is Planck's constant, and f is frequency). The nature of the target material can also affect the X-ray spectrum. Different target materials can produce X-rays with different characteristics, such as their intensity and distribution of wavelengths. So, both the accelerating potential (b) and the nature of the target (c) play a role in determining the frequency of X-rays, making option (d) "Both b and c" the correct choice.