Photon Energy

E = \dfrac {hc}{\lambda}

  • E is Energy in Joules
  • h is Planck’s constant, which has units of J \cdot s
  • c is the speed of light, with units of m/s
  • \lambda is wavelength and its units are m

We will test the units on both sides of the equation.

  • For the left side, E has the units of J.
  • J = N \: m = \dfrac {kg \: m \: m} {s^2} = \dfrac {kg m^2} {s^2}
  • For the right side, \dfrac {J \: s \dfrac {m}{s}}{m} = \dfrac {J \: \dfrac {s \: m}{s}}{m} = \dfrac {J \dfrac {m}{1}}{m} = \dfrac {J m}{m} = J

. .. …

Both this equation and the

Einstein Equation solve for E so we can put them together:

E = E

m \:c^2 = \dfrac {h \: c} {\lambda}

m \: c = \dfrac {h} {\lambda}

\lambda \: m \: c = h

\lambda = \dfrac {h} {m \: c}

More resources below…

  • Einstein Equation
  • Snell’s Law
  • Light