The penetrating power of X-rays increases with:

Explanation

Option A: The velocity of an X-ray is not directly related to its penetrating power. In fact, the velocity of an X-ray can actually decrease as its energy increases, because the higher-energy X-rays are more likely to interact with matter and be absorbed. Option B: The penetrating power of X-rays increases with an increase in frequency. This is because the frequency of a wave is directly proportional to its energy, and the energy of an X-ray is what determines its ability to penetrate matter. Therefore, X-rays with a higher frequency will have a greater penetrating power than X-rays with a lower frequency. Option C: The velocity of an X-ray is not directly related to its penetrating power. However, in general, the velocity of an X-ray will increase as its energy increases. Therefore, X-rays with a higher energy will also have a higher velocity. Option D: The intensity of an X-ray is a measure of the number of X-rays per unit area. It does not have a direct effect on the penetrating power of X-rays. In fact, the intensity of an X-ray beam can actually decrease its penetrating power, because the more X-rays there are, the more likely they are to interact with matter and be absorbed.