Planck determined the relationship between the energy of a photon and its frequency (recall that photons travel as waves). This relationship is expressed as Planck's constant: h= 6.626 x 10-4 J-s This means that we can find the energy of a photon if we know its frequency: Where: E is the energy of the photon in J his Planck's constant, 6.626 x 10-34 J-s v is the frequency in s (note: "v" is the Greek letter nu) We also know that the product of a wave's frequency and wavelength are equal to the speed of light: E = hv Where: c is the speed of light, the constant 2.998 x 10 m/s A is the wavelength in m v is the frequency in s These relationships can be combined to make the equation: E = 1) What is the energy of a photon of red light that has a wavelength of 715 nm (1 m = 1 x 10 nm)? c =