Category Archives: physics

the Gaussian beam (interactive)

The Gauss­ian beam “is a con­ve­nient, wide­spread mod­el in laser optics.” [1] It is indeed con­ve­nient that such a math­e­mat­i­cal­ly rel­a­tive­ly sim­ple mod­el can describe the evo­lu­tion of laser light in free space so well. Giv­en the wave­length of the laser, it can be described by a sin­gle para­me­ter. This can be either the beam […]

the Doppler effect (relativistic)

Chris­t­ian Doppler in 1942 pre­dict­ed the Doppler effect for all kinds of waves, not only sound waves. The Doppler effect for light was demon­strat­ed in 1948 by Fizeau. In con­junc­tion with the arti­cle on the clas­si­cal Doppler effect, as it occurs e.g. for sound waves, we will here exam­ine the rel­a­tivis­tic Doppler effect which is […]

the Doppler effect (classical)

The Doppler effect is noth­ing real­ly new. It’s well-known that Doppler fre­quen­cy shift occurs for sound as well as light; there are, how­ev­er, some sub­tle dif­fer­ences between the two, owing main­ly to Einstein’s spe­cial the­o­ry of rel­a­tiv­i­ty. This arti­cle describes the clas­si­cal Doppler effect as it occurs e.g. for sound waves and in which the […]