The ionization potentials of HI and KI are 13.6 and 4.3 ev. Calculate the wavelengths of photons that can ionize HI and KI. Calculate the photospheric temperatures of stars that peak at these wavelengths, and hence radiate plenty of photons at shorter wavelengths capable of ionizing these atoms. First, I calculated the wavelengths using e=(hc)/lambda . I have lambda=(hc)/13.6 and lambda=(hc)/lambda . Now what do I do next? Any suggestions are welcome! Thanks in advance!