For the same amount of energy, the number of photons in red light will be greater than the number of photons in blue light. This is because the energy carried by a photon is inversely proportional to the wavelength of the photon. A longer wavelength means there is a lower energy in the photons and a shorter wavelength means that there is a higher energy. Therefore, in order for the photons to deliver one joule of energy, more of the red light photons will be required.
what Is the number of photons in one J of red light (650 nm) greater than, equal to, or less than the number of photons in one J of blue light (450 nm)?