So when it comes to calculating the energy of light in the form of a photon, we have two different formulas that we can rely on and realize. Only one of them has a purple box around it. So that one is the more commonly used formula, and that's the one you should keep in mind and memorize. So we're going to say here the first version is used when we deal with energy and frequency. So here it's going to say that change in energy or energy of a photon in joules per photon equals Planck's constant which is H times frequency which is in seconds, inverse or Hertz. So remember frequency uses the on Greek symbol MU.
Now the other one we use when we're dealing with calculating the energy of a photon when given energy and wavelength in this one we're going to say change in energy or energy of a photon in joules over photons equals Planck's constant still, but now it's times the speed of light divided by wavelength in meters. So just remember two different formulas, one we use when we're dealing with frequency and energy and the other one we use when we're dealing with wavelength and energy.
Now from the equations realize that this tells us that energy is directly proportional to frequency. Meaning that if your energy is going up, your frequency is going up and it would be inversely proportional, inversely proportional to wavelength. That means that if your energy or frequency are increasing, that means wavelength would have to be would have to be decreasing. So just keep in mind the relationships that we have between now energy, frequency and wavelength.
E = h ν E = h c λ