Millikan, in 1909, determined the charge on electron by the apparatus consisting of a metallic chamber having two parts. The chamber is filled with air whose pressure can be adjusted by a vacuum pump. There are two electrodes A and A’. These electrodes are used to generate an electrical field in the space between the…
i) In order to measure the e/m value of electrons J.J Thomson in 1897 devised an instrument consisting of a discharge tube. ii) The cathode rays are allowed to pass through electric and magnetic fields. iii) When both the fields are off, the beam of cathode rays consisting of electrons produce bright luminous spot at…
As the atom was considered neutral, therefore, soon after the discovery of negatively charged particles i.e., electrons, scientists tried to discover a positively charged constituent of atom. In 1886, Eugene Goldstein used a discharge tube with perforated cathode. He observed a glow in the region behind the cathode. This glow was consequence of rays, which…
To study the properties of cathode rays systematic investigations were made by W. Crooks, J.J. Thomson and J. Perrin. They established the following properties of cathode rays: Cathode rays are negatively charged. In 1895, J.Perrin showed that cathode rays are deflected in a magnetic field perpendicular to the line joining the two poles. In 1897,…
Discharge tube The discharge tube is a glass tube having two electrodes sealed into it connected to a vacuum pump to reduce the pressure of the gas taken into it. A slit is placed in the tube to get a sharp beam of radiations. Experiment: William Crooks a British scientist studied the passage of electricity…
According to Greek philosophers, matter is composed of very small particles which cannot be further divided. DEMOCRITUS (460-370BC) named these particles as atoms derived from a Greek word “ATOMOS” which mean indivisible. The ideas of Greek philosophers were not experimental based. In the late 17th century, the quantitative analysis of many substances disclosed that they…