A photon of X-ray has energy of 1 keV. A photon of visible radiation has energy of 3 eV. In this context, which one of the following statements is not correct? A. The wavelength of X-ray photon is less than the wavelength of visible radiation photon. B. Both the photons have different energies. C. The speeds of both the photons in vacuum are different D. The frequency of X-ray photon is higher than the frequency of visible radiation photon.

The correct answer is: C. The speeds of both the photons in vacuum are different.

The speed of light in vacuum is a constant, $c=299,792,458$ m/s. This means that all photons, regardless of their energy, will travel at the same speed in vacuum.

The wavelength of a photon is inversely proportional to its energy, so a photon with higher energy will have a shorter wavelength. The frequency of a photon is proportional to

Therefore, the correct answer is C. The speeds of both the photons in vacuum are different.