If the energy is given...
If, on the other hand, the energy is given and you are to obtain the wavelength, first rearrange Eq (IV) to isolate the unknown quantity (? ) on the left side:
(found by multiplying both sides of IV by ? and dividing both sides by E)
Now substitute in numerical values for h, c, and E into Eq. (V) and you obtain a numerical result for the wavelength .