# I When can Klein-Gordon Equation be used for photon?

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1. Mar 7, 2017

### referframe

Consider the double-slit experiment done with photons from a laser. If one was interested only in computing position (vertical) probability amplitudes and did not care about spin/helicity, could the Klein-Gordon Equation (with mass set to zero) be used?

Last edited: Mar 7, 2017
2. Mar 7, 2017

### dextercioby

The Klein-Gordon equation for a (wave)function reads: $(\square +m^2) \phi (x) =0$ and applies for a massive photon, too (massive electromagnetic field). Drop the mass term and you've got the D'Alembert equation (the e-m potential satisfies this equation in the covariant Lorenz gauge).

Did you read a book about the scalar diffraction theory in optics?

3. Mar 7, 2017

### bhobba

Last edited by a moderator: May 8, 2017
4. Mar 8, 2017

### referframe

Not yet. Can you recommend a good one?