[Physics Class Notes] on Hertz Lenard Observations Pdf for Exam

It was in 1887 when Heinrich Hertz was conducting experiments to prove Maxwell’s electromagnetic theory of light, that he noticed a phenomenon which is strange. Hertz generally used a gap of spark – two sharp electrodes that are placed at a distance which is small so that spark of electricity can be generated that is to detect the presence of waves which are electromagnetic. To get an even closer look he placed it in a box that was dark and found that the length of the spark was reduced. When he used a box of glass then the spark length increased and when he replaced it with a box of quartz the length of the spark increased further. This was the observation which was the first of the effects of photoelectric.

A year later we can say that Wilhelm Hallwachs generally confirmed these results and showed that light which was the UV light on a Zinc plate that is connected to a battery generated a current that is because of electron emission.  J.J. Thompson in 1898 found that the amount of current varies with the frequency and intensity of the radiation that is used.

Later in 1908, Lenard Observed that the kinetic energy of electrons which are emitted increased with the frequency of radiation that is used. This could not be explained as the theory of Maxwell’s electromagnetic which Hertz proved correct, predicted that the energy which is kinetic should be only dependent on light intensity and not on the frequency.

The resolution which we have discussed would only come a few years later that too from famous scientist  Einstein when he would provide an explanation to the Photoelectric Effect.

Hertz Lenard Observations

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To test the hypothesis of Maxwell’s Hertz that is used, an oscillator which is made of polished brass knobs that each one is connected to an induction coil and separated by a tiny gap that is over which sparks could leap. To confirm this whole thing that we have discussed, Hertz made a simple receiver of looped wire. Its ends are separated by a tiny gap as we will notice this. The receiver present was placed several yards from the oscillator. Hertz reasoned that if Maxwell’s had the predictions which were said to be correct, electromagnetic waves would be transmitted during each series of sparks that would induce a current which is in the loop that would send the sparks that too across the gap. This generally occurred when Hertz turned on the oscillator and produced the first reception and the transmission of electromagnetic waves. Hertz also noted that a conductor which is electrical reflects the waves and that they can be focused that too by a reflector that is concave. He found that the nonconductors generally allow most of the waves to pass through. The phenomenon of photoelectric emission was discovered in the year 1887 by Heinrich Hertz during the electromagnetic wave experiments. He generally observed that when the light falls on a surface of a metal, some of the electrons that are near the surface absorb energy which is enough from the incident radiation to overcome the attraction which is of the positive ions which are in the material of the surface.

Hertz and Lenard’s Observations of the Photoelectric Effect

This observation that we have seen that is related to the effect which is photoelectric and how this effect is proven by two scientists is one of the experiments that was conducted in 1887 by Heinrich Hertz to prove the theory of electromagnetic light when he observed strange phenomena as he placed two electrodes at a very small distance. So we can say here that an electric spark can be generated and he used a spark gap to apply this experiment so that he can easily observe the presence of waves which are electromagnetic. The same which we can say is the case with Lenard as he observed the kinetic energy of electrons which are emitted and then increased with the radiation that is used. Both of their experiments show the different types of samples or we can say that the experiment to prove the same thing but they all were given green signals and only when this was confirmed and proven by Einstein.

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Every metal that we have learnt consists of certain minimum frequency which is of incident radiation below which no photoelectrons are emitted or are not able to emit this type of frequency is known as the threshold frequency The increasing frequency of the beam which is incident keep the number of photons that are fixed and this would keep the proportionate increase in energy and also this increases the kinetic energy to its maximum and leads to stopping the voltage which is increased. It is also generally mentioned that if the intensity which is of the radiation that is incident is said to be increased when there will be no effect on the kinetic energy of photoelectrons as kinetic energy depends upon the frequency that is of light and thus, the level of energy provided by each photon. On the other hand, we can say that stopping the voltage does not depend on the intensity of the light but we can say that it is generally provided with the light frequency that is to be fixed at a point.

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In a subject like physics, kinetic energy is the energy that is possessed by an object which is moving or by its motion. In other words, we can say that it can be defined as work which is required by a body which is to accelerate from its actual position to the position it wants to reach and the body which keeps this kinetic energy until and unless it changes its speed. Same goes with the case of accelerating the body which is from moving at a speed that is to divert itself towards the rating part. It is said that the energy that generally occurs in many forms which include energy which is chemical or we can also say the thermal energy and the electromagnetic energy that includes nuclear energy and rest energy and many more can be added to this category. Thus, kinetic energy can be seen in a moving object and also in the resting one.