WAVE NATURE OF ELECTRON orpuscles per unit volume around that point). This hypothesis is necessary to explain how, in the case of light interferences, the light energy is con- centrated at the points where the wave intensity is maximum: if in fact it is assumed that the light energy is carried by light corpuscles, photons, then the photon density in the wave must be proportional to the intensity This rule in itselfwill enable us to understand how it was possible to verify the wave theory of the electron by experiment Let us in fact imagine an indefinite cloud of electrons all moving at the ame velocity in the same direction. In conformity with the fundamental ideas of wave mechanics we must associate with this cloud an indefinite plane wave of the form 「W,xx+By+ asmn2元 Lh where apy are the cosines governing the propagation direction and where he wavelength A is equal to ly/p. With electrons which are not extremely d hend where mo is the rest mass of the electron You will be aware that in practice, to obtain electrons moving at the same velocity, they are made to undergo a drop in potential P and we have h lly this gives I2.24 10-8 cm (Pin volts)WAVE NATURE OF ELECTRON 253 corpuscles per unit volume around that point). This hypothesis is necessary to explain how, in the case of light interferences, the light energy is con￾centrated at the points where the wave intensity is maximum: if in fact it is assumed that the light energy is carried by light corpuscles, photons, then the photon density in the wave must be proportional to the intensity. This rule in itselfwill enable us to understand how it was possible to verify the wave theory of the electron by experiment. Let us in fact imagine an indefinite cloud of electrons all moving at the same velocity in the same direction. In conformity with the fundamental ideas of wave mechanics we must associate with this cloud an indefinite plane wave of the form where aby are the cosines governing the propagation direction and where the wavelength 1, is equal to h/p. With electrons which are not extremely fast, we may write and hence where m. is the rest mass of the electron. You will be aware that in practice, to obtain electrons moving at the same velocity, they are made to undergo a drop in potential P and we have Hence, Numerically this gives