G.P Thomson Experiment

Contents

Introduction

Blackbody radiation

Planck’s quantum theory

Photoelectric effect

Problems on photoelectric effect

De-Broglie hypothesis

Problems on De-Broglie hypothesis

G. P. Thomson experiment

Wave function

Time independent Schrodinger equation

Particle in one dimensional box

Problems on one dimensional box

Heisenberg Uncertainty principle

Previous Years' Questions

1 Mark Questions

Quiz 1

Quiz 2

The existence of waves associated with moving particle confirmed by G.P. Thomson experiment.
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Construction and working principle

It consists of a discharge tube in which the electrons are produced from the cathode C.The electrons are accelerated by potential upto 50,000 volts. These accelerated electrons are passed through a slit S to obtain a fine beam of electrons.Then,they are allowed to fall on a very thin metallic film G of gold foil. The thickness of the film is of the order of 10-6 cm. The whole apparatus is exhausted to a high vacuum so that the electrons may not lose their energy in collision with the molecules of the gas. The electron beam coming out of the foil is recorded the photographic plate P. After developing the plate, a symmetrical pattern of concentric rings about central spot diffraction pattern is obtained.This pattern is similar to pattern produced by x-rays.

The diffraction pattern can only be produced by waves and not by the particles. To make sure that this pattern is due to the electrons and not due to any possible X-ray generated, the cathode rays in the discharge tube are deflected by magnetic field. This is confirmed that the diffraction pattern is only due to the electrons. So Thomson concluded that electrons behaved like waves. He also calculated the associated wavelength of electrons. It found that the wave length of electron depends only on the accelerating voltage and it is independent of the nature of the target material.