The photoelectric effect is caused by the absorption of electromagnetic radiation and consists of electron ejection from a solid or liquid surface, usually of a metal, though nonmetals have also been studied. In the case of a gas, the term photoionization is more… Discovery and early work The photoelectric effect was discovered in by the German physicist Heinrich Rudolf Hertz. In connection with work on radio waves, Hertz observed that, when ultraviolet light shines on two metal electrodes with a voltage applied across them, the light changes the voltage at which sparking takes place.
Discussion dilemma Under the right circumstances light can be used to push electrons, freeing them from the surface of a solid.
This process is called the photoelectric effect or photoelectric emission or photoemissiona material that can exhibit this phenomena is said to be photoemissive, and the ejected electrons are called photoelectrons; but there is nothing that would distinguish them from other electrons.
All electrons are identical to one another in mass, charge, spin, and magnetic moment. The photoelectric effect was first observed in by Heinrich Hertz during experiments with a spark gap generator the earliest device that could be called a radio. In these experiments, sparks generated between two small metal spheres in a transmitter induce sparks that jump between between two different metal spheres in a receiver.
Compared to later radio devices, the spark gap generator was notoriously difficult to work with. The air gap would often have to be smaller than a millimeter for a the receiver to reliably reproduce the spark of the transmitter. Hertz found that he could increase the sensitivity of his spark gap device by illuminating it with visible or ultraviolet light.
Later studies by J. Thomson showed that this increased sensitivity was the result of light pushing on electrons — a particle that he discovered in While this is interesting, it is hardly amazing.
All forms of electromagnetic radiation transport energy and it is quite easy to imagine this energy being used to push tiny particles of negative charge free from the surface of a metal where they are not all that strongly confined in the first place.
The era of modern physics is one of completely unexpected and inexplicable discoveries, however. Subsequent investigations into the photoelectric effect yielded results that did not fit with the classical theory of electromagnetic radiation.
When it interacted with electrons, light just didn't behave like it was supposed to.
Repairing this tear in theory required more than just a patch. It meant rebuilding a large portion of physics from the ground up. It was Philipp Lenardan assistant of Hertz, who performed the earliest, definitive studies of the photoelectric effect.
Lenard used metal surfaces that were first cleaned and then held under a vacuum so that the effect might be studied on the metal alone and not be affected by any surface contaminants or oxidation.
The metal sample was housed in an evacuated glass tube with a second metal plate mounted at the opposite end. The tube was then positioned or constrained in some manner so that light would only shine on the first metal plate — the one made out of photoemissive material under investigation.
Lenard connected his photocell to a circuit with a variable power supply, voltmeter, and microammeter as shown in the schematic diagram below. He then illuminated the photoemissive surface with light of differing frequencies and intensities.
Knocking electrons free from the photoemissive plate would give it a slight positive charge. Since the second plate was connected to the first by the wiring of the circuit, it too would become positive, which would then attract the photoelectrons floating freely through the vacuum where they would land and return back to the plate from which they started.
Keep in mind that this experiment doesn't create electrons out of light, it just uses the energy in light to push electrons that are already there around the circuit.
The photoelectric current generated by this means was quite small, but could be measured with the microammeter a sensitive galvanometer with a maximum deflection of only a few microamps.
It also serves as a measure of the rate at which photoelectrons are leaving the surface of the photoemissive material. Note how the power supply is wired into the circuit — with its negative end connected to the plate that isn't illuminated.
This sets up a potential difference that tries to push the photoelectrons back into the photoemissive surface. When the power supply is set to a low voltage it traps the least energetic electrons, reducing the current through the microammeter.
Increasing the voltage drives increasingly more energetic electrons back until finally none of them are able to leave the metal surface and the microammeter reads zero. It is a measure of the maximum kinetic energy of the electrons emitted as a result of the photoelectric effect.
What Lenard found was that the intensity of the incident light had no effect on the maximum kinetic energy of the photoelectrons.Photoelectric Effect Lab Abstract We used a photoelectric effect to determine the Planck’s constant.
Using a mercury lamp, varying filters and varying voltages we measured the output current. Using a mercury lamp, varying filters and varying voltages we measured the output current.
Photoelectric effect photoelectric effect is the process of emission of electron from the surface of metal when a photon of certain frequency is incident to a metal surface. Tthe electron committed is called photon electron. The photoelectric effect is a quantum electronic phenomenon in which.
Photoelectric effect, or photoelectric absorption (PEA) is a form of interaction of X-ray or gamma photon with the matter. A low energy photon interacts with the electron in the atom and removes it from its shell.
The probability of this effect. Compton scattering, discovered by Arthur Holly Compton, is the scattering of a photon by a charged particle, usually an electron.
It results in a decrease in energy (increase in wavelength) of the photon (which may be an X-ray or . Photoelectric effect: Photoelectric effect, phenomenon in which electrically charged particles are released from or within a material when it absorbs electromagnetic radiation.
The effect is often defined as the ejection of electrons from a metal plate when light falls on it. In a broader definition, the radiant energy.
These interactions include the photoelectric effect, scattering, and pair production. The figure below shows an approximation of the total absorption coefficient, (µ), .