Contents Introduction: 2 What is the photoelectric effect? 2 Origin of the photoelectric

One of J.J. Thomson's most significant contributions to science, and thus to the study of atomic theory, was his discovery of the electron. Before the discovery of the electron, the atom was already associated with having electric charges-both positive and negative-but the idea of an electron existing as its own particle was unheard of. It was in 1897 when Thomson first conducted the beginning of his now famous experiment, in which he used a cathode ray tube to aid in his findings. A cathode ray tube, is a vacuum tube in which cathode rays, negatively charged particles, are produced at the cathode and travel through the vacuum, which is created when gas is extracted from the tube. J.J. Thomson discovered that in order to determine

     In 1954 Bell Laboratories invented the first photovoltaic (or solar) cell, made from the semi-conductor silicon, and other elements. It was the first way to convert sunlight directly into electricity. When the space program was launched in the 60's, it

In paragraph eleven of "Energy Story" it explains how electrons can work. The author states "Electrons can be made to move from one atom to another." and continues to "When

- I think that the electrons that are emitted from the cathode are emitted with a range of velocities (perhaps like a Boltzmann distribution where average speed clusters in the middle of the range).

When light is absorbed the electrons get excited and go into a higher energy level, so it move much more freely. This produces an electrical

1895 – X-rays were discovered accidentally by physicist Wilhelm Conrad Rontgen. Rontgen was working on a experiment and testing whether cathode rays could pass through glass. He noticed that a nearby tube emitted fluorescent glow of crystals. The air in the tube was released, high voltage applied, the same tube emitted a fluorescent glow. When Rontgen covered the tube in a heavy black paper, a green light could be seen. He concluded that a new light ray was being broadcast. Rontgen discovered that the light was very powerful and the same ray could pass through human tissue, but not through bones and metal objects. Medical applications were soon to follow. ("History of radiography," )

In 1915, the 5th November in Tonopah, Nevada; Hugh Bradner was born. Brother to Mead Bradner, and children to both Donald Bradner and Agnes Bradner (maiden name Mead). He and his brother were raised in Findlay, Ohio, and had done most schooling there. After high school, Hugh decided to study at Miami University in 1936. Hugh chose to study in the fields of Engineering, geophysics, and physics. Further on in life, he had received his doctorate from California Institute of Technology in 1941. He had written a thesis on “Electron-optical of the photoelectric effect” under guidance from William Houston.

The greatest energy that can be produced by the sun is electricity. Photovoltaics, or solar cells, capture the sun and convert it into electricity. Solar cells were discovered by the Europeans back in the 1870’s when they used selenium to develop the telegraph. They found that when light hits selenium it would produce and electrical current. Soon enough there were many scientists and engineers working on photovoltaic systems. Silicon and Selenium proved to be the two best elements to conduct electricity when light hits them. Photovoltaic systems (PV cell) work by converting the suns light into electricity. A semi conducting material absorbs the sunlight, that energy knocks electrons loose from their atoms, this allows the electrons to flow through the material to produce electricity. The further development of solar cells can be attributed to the satellite industry. Solar cells were expensive and there was no use for them until satellites came. Because it is impractical to tether satellites it became important to develop solar energy at any cost that would power these satellites. This created a sustainable market for solar power, the first of its kind.

Thomson discovered the electron. He used a cathode ray tube (an electron gun) with a magnet and discovered that the green beam it emitted was made up of negatively charged particles. Thomson then determined that these negatively charged electrons needed something positive to balance them out. (Born, 2014)

X-rays were discovered by accident in 1895 by the German physicist Wilhelm Conrad Roentgen. Roentgen was already an accomplished scientist with forty-eight published papers. He had a reputation among the scientific community as a dedicated scientist with precise experimental methods. Roentgen had been conducting experiments at the University of Wurzburg on the effect of cathode-rays on the luminescence of certain chemicals. Roentgen had placed a cathode-ray tube, which is a partially evacuated glass tube with metal electrodes at each end, in a black cardboard box in his darkened laboratory. He sent electricity through the cathodre-ray tube and noticed something strange his laboratory. He saw a flash of light

Electromagnetic radiation is the term used to describe the different types of energy that are released into space. The Compton effect is when high energy protons collide (x-rays) with a target and transfer energy to a single electron. This research of his supported Albert Einstein's theory of light, E=mc². On behalf of his research and the discovery of the Compton Effect he was awarded the Nobel Prize in 1927 for his work in physics. For being such a valuable physicist Arthur was recognized by the government and recruited to work on the top secret assignment, The Manhattan Project. The Manhattan Project was a research and developmental project to create the world’s first nuclear bomb. Arthur Compton died on Thursday, March 15, 1962 in Berkeley, California because of an intracerebral hemorrhage (an unpredicted accident when a diseased blood vessel ruptures in the brain creating damage or death). Arthur Compton’s doing on the Manhattan Project with using atoms to create the first nuclear bomb will forever be an important part of

During the cold winter of 1895, a German scientist by the name of Wilhelm Conrad Roentgen was working with a cathode-ray tube when he noticed nearby crystals were glowing. When Roentgen reached for the crystals he was amazed when the shadow cast on the crystal was not of his whole hand, but just his bones. Roentgen covered the tube with heavy black paper and saw that the crystals still glowed and the shadow of his hand bones still shown through, he then determined that a new ray was being emitted that could penetrate through thick materials. (1.) He later found that the rays could pass through most anything, but would cast a shadow of solid objects; these shadows could then be captured on film. Among the solid objects Roentgen shot with

Many centuries ago people did not need much energy. Back then, people used the sun or burned wood and straw for heat. People used the wind force in sails or horses to go anywhere in the world and used animals to do the work humans could not do. Although, humans did use simple machines that could ground grain, pump water, and even utilize steam power. Steam engines transformed over time and by the 18th century the modern steam engine, fueled by coal, could do the job of a team of horses. Since steam engines were much more favorable compared to air and wind power, steam engines were used to power factories and coal was used to heat up buildings.

Originally electricity and magnetism were thought of as two separate forces. This view changed, however, with the publication of James Clerk Maxwell's 1873Treatise on Electricity and Magnetism in which the interactions of positive and negative charges were shown to be regulated by one force. There are four main effects resulting from these interactions, all of which have been clearly demonstrated by experiments:

The threshold frequency varies with each metal. When the sodium plate was exposed to high frequency light, electrons were emitted and were attracted to the positive terminal, causing a flow of current. However, when a low frequency light was used no electrons were emitted and therefore there was no current. Observations of the Photoelectric Effect 1. Current flows as soon as the negative terminal is illuminated.