1 / 9

The discovery of photoelectricity

The discovery of photoelectricity. Photoelectricity was first discovered in 1887 by Heinrich Hertz during investigations into radio waves using a “spark gap”. Radio waves are produced when a high voltage is supplied across two electrodes causing a spark in the gap.

akiva
Download Presentation

The discovery of photoelectricity

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The discovery of photoelectricity Photoelectricity was first discovered in 1887 by Heinrich Hertzduring investigations into radio waves using a “spark gap”. Radio wavesare produced when a high voltage is supplied across two electrodes causing a spark in the gap. Hertzfound that if ultravioletlight was shone on the electrodes, the sparks were much stronger and thicker.

  2. Measuring photoelectricity In the late 19th century, scientists used apparatuses like this photocell to analyze and measure photoelectricity. photocell When light is shone on the cathode of the photocell, electrons are released. They are attracted to the anode, causing a current to flow. anode cathode vacuum

  3. The gold leaf electroscope

  4. Photon energy In 1905, Albert Einstein published a paper that described his photon theory of light. This explained experimental evidence, such as the photoelectric effect, that did not fit with the classical wave model of light. Einstein proposed that, although light exhibited wave-like properties, it traveled in particles called photons. He explained that photons contain discrete “energy packets” called quanta, and that the energy of an individual quantum depends on the frequency of the light.

  5. Einstein’s photoelectric equation

  6. The photoelectric effect equation

  7. More about Photons Niels Bohr used Einstein's concept of photons to establish electron orbits. Electrons are really pretty lazy and like to exist in the lowest energy level possible – ground state. These are the orbits closest to the nuclei and they fill first as you move across the elements in the periodic table. Electrons that absorb a photon of energy jump to a higher energy orbit. Eventually, the electron will give off energy to get back to ground state and will release the photon of energy.

  8. Photons and frequencies An electron can absorb more than one photon of energy As the electron gives off one or more photons to get back to ground, each change in energy corresponds to a distinct measurable frequency of light. The same frequencies of light are what excite the electrons. One application of the photoelectric effect is solar panels. The panels contain photocells, which flow with DC when the electrons excited by the sunlight emit photons.

More Related