GP THOMSON EFFECT - Experimental Verification of Wave nature of Matter

G P  Thomson has performed experiments with electrons accelerated from 10000 to 50000 volts.

The high energy beam of electrons is produced by a cathode ‘C’.

The experimental arrangement is as shown below:

The electron beam is excited with potential upto a maximum of 50,000 volts. A fine beam is obtained by passing it through slit or diaphragm ‘S’.

The accelerating fine beam of electrons now falls on thin gold or Aluminum film (order of 10-6 cm thickness).

The photograph of beam from foil is recorded on photographic plate ‘P’.

After developing the plate, a symmetric pattern consisting of concentric rings about a central spot is obtained. This pattern resembles that of X- rays.

To know that this pattern is due to electrons or due to x-rays generated by electrons in their passage through foil, cathode rays in discharge tube are deflected by magnetic field.

It was observed that beam shifts correspondingly showing there by that pattern is produced by electrons and not by x-rays.  (i.e X – ray pattern is not affected by electric and magnetic fields).

As diffraction pattern can only be produced by waves and not by particles, so Thomson concluded that electrons behave like wave.

Thus, Thomson experiment clearly demonstrated the existence of matter waves.

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