Hallwachs Experimentset-up
Experimentset-up to study the photo electric effect is shown in Fig. It consists of an evacuated quartz bulb with two zinc plates cathode and anode. The plates are connected to a battery and a sensitive galvanometer. In the absence of any radiation incident on the plates.There is no flow of current and hence there is no deflection in the galvanometer. But,when an electro magnetic radiation like ultraviolet radiation is allowed to fall on the cathode plate which is connected to the negative terminal of the battery, a current begins to flow,indicated by the deflection in the galvanometer But, when ultraviolet radiation is made to fall on anode there is no deflection in the galvanometer. These observations reveal that the particles emitted by the cathode plate due to the photoelectric effect are negatively charged. These particles were found to be electrons. The observed current known as the photoelectric current is due to the flow of electrons.After the study of photoelectric effect by Hallwachs, scientists J.J.Thomson, Lenard, Richardson, Compton did a series of experiments to study the relationship between photoelectric current, intensity ofincident radiation, velocity and the kinetic energy of the photo electrons, and their dependence on the wave length of incident radiation used.
Experimentset-up to study the photo electric effect is shown in Fig. It consists of an evacuated quartz bulb with two zinc plates cathode and anode. The plates are connected to a battery and a sensitive galvanometer. In the absence of any radiation incident on the plates.There is no flow of current and hence there is no deflection in the galvanometer. But,when an electro magnetic radiation like ultraviolet radiation is allowed to fall on the cathode plate which is connected to the negative terminal of the battery, a current begins to flow,indicated by the deflection in the galvanometer But, when ultraviolet radiation is made to fall on anode there is no deflection in the galvanometer. These observations reveal that the particles emitted by the cathode plate due to the photoelectric effect are negatively charged. These particles were found to be electrons. The observed current known as the photoelectric current is due to the flow of electrons.After the study of photoelectric effect by Hallwachs, scientists J.J.Thomson, Lenard, Richardson, Compton did a series of experiments to study the relationship between photoelectric current, intensity ofincident radiation, velocity and the kinetic energy of the photo electrons, and their dependence on the wave length of incident radiation used.
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