Einstein's Equation
Part of the Optics, Waves and Modern Physics section of Coddy's Physics journey. Lesson 36 of 53.
The photon's energy hf goes to one electron; getting out costs at least W.
Kmax = hf − W
400 nm on sodium: 3.11 eV per photon, so Kmax = 3.11 − 2.3 = 0.81 eV.
Challenge
Light of wavelength 400 nm falls on sodium (W = 2.3 eV). First find the photon energy E, then the largest kinetic energy K of the electrons, in eV.
Try it yourself
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Optics, Waves and Modern Physics
1Reflection and Refraction
Reflection of LightThe Refractive IndexSnell's LawTotal Internal ReflectionDispersionApparent DepthRecap - Optical Fiber4Mechanical Waves
What a Wave IsTwo Graphs of a WaveWhen Pulses MeetInterferenceStanding WavesHarmonicsRecap - Guitar String7Photons
Light Comes in PhotonsThe Photoelectric EffectEinstein's EquationStopping VoltageCounting PhotonsRecap - Solar Cell