Photoelectric effect is the process by which electrons are emitted from the surface of a photosensitive material when hit by light incidents. The intensity of the light energy determines the kinetic energy of the produced photoelectrons. …
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This is described in a classical wave model of light; which states that light properties that are similar to any wave. For instance, light experiences reflection and refraction in the same manner that any other wave would experience interference. In addition, light experiences the Doppler effect the same way any other wave would experience Doppler effect. However, the prediction of the quantum model shows that frequency or wavelength of the incident of the incident light only affects the photoelectric current. where E- is the energy that the quantum light produces, Kmax is the maximum kinetic energy of the photoelectrom emitted , where as Wo is the work function of the of the energy needed to innitiate the emision of photoelectrons from the metal surface. In an experiment to demonstrate the photoelectric effect, the following apparatus are required: a digital voltmeter to be used to measure the reverse voltage reading, a photodiode connected with an amplifier, monochromatic light source to produce light beams to irradiate the photo cathode, and a filter to neutrally vary the intensity of light. Generally the quantization energy of the electromagnetic radiation in light is given in the relation, where the radiation energy, is a constant known as the Plank’s constant and is given as (6.63?10^-34Js), and - is the frequency of the light incident energy. The validity of the equation is based on the photoelectric effect experiment. There are four aspects that need to be taken into consideration when conducting the photoelectric effect experiment. These facts include: the minimum frequency; when the frequency of the incident light is less than the minimum frequency required, no photoelectrons can be emitted despite the intensity of the light. The value of minimum frequency varies from metal to metal. Secondly, as the frequency of the incident light increases, the kinetic energy of the photoelectrons increases. However, the intensity of the light is independent of the kinetic energy of the electron emitted. And lastly, the emission of photons is effectively instantaneous. (physics 242 laboratory manual) The photoelectric effect experiment consists if a high intensity lamb, a phototube, and batteries. The photodiode tube is the central element of the apparatus. The window in the diode gives way for light into the tube to the clean metal surface at the cathode. The diode is completely evacuated to avoid any collision of air molecules and the electrons. When beams of light hit the surface of the metal plate at the cathode, electrons are emitted by the metal plate. The photodiode has an in-built capacitance developing a voltage during the charging process by the electrons emitted. When the stopping potential of the cathode is reached, the difference in voltage across the two poles, that is, cathode and anode stabilizes. A very sensitive amplifier is used to measure the stopping potential. The amplifier aids in the establishment of the small number of photoelectrons emitted. A voltmeter is used to measure the output voltage of the between the batteries and the output ground terminals. A number of different monochromatic light beams are used for the experiment. A glass tube consisting of mercury vapor produces light when discharged electrically. The glasses envelop filters out the ultraviolet light that can be harmful. The mercury light produces five thin spectral lines that are: yellow, green blue, violet, and ultraviolet in the visible region. These lines can be spatially separated by diffraction. The wavelength desired is selected using a collimator, and the intensity of the selected wavelength is varied using a density filter The mercury lamb is switched on. On the front reflective mask of the lamb box, yellow, green, and tiny rays of blue
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The above micrographs represent a Secondary electron image (SE) and a Backscatter electron image (BSE) of the same region of an asbestos sample.The SE image appears more three dimensional than the BSE image. The cluster of fibers at the center in the SE image appears more rounded, while the one in the BSE appears flat.
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This essay analyzes that spherical aberration also occurs in the Electron Microscopes when electrons passing through the side of the lens are refracted greater than those passing along the axis.2 (Lam, 2009); while Diffractive aberrations are brought about by the deviations from geometrical optics caused by the wave nature of light.
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