Atomic Spectra report - Atomic Spectra Li Cheuk Kwan Jeremy...

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Atomic Spectra Li Cheuk Kwan Jeremy A0081231W B04 1 Introduction Bohr’s theory prescribes that electrons move in circular orbits around the nucleus due to the Coulomb force between the negative electrons and the positive nucleus. However, the orbits have discrete energy levels, and therefore only electrons with the same amount of energy as the energy level of the orbit can reside in the orbit. An electron within an allowed orbit does not radiate energy and this is said to be in a stationary state. The for hydrogen atoms, the energy of the nth level can be described by where m is the mass of an electron, e the charge of an electron, h the plank’s constant, and the electrical permittivity of free space. Instead, energy is radiated by the atom only when an electron makes a transition from an allowed orbit to another, and the energy radiated by the atom is in the form of a photon of energy hf where f is the frequency of the photon. The energy radiated can be related to the wavelength of the photon and the orbit n of the electron responsible n in the following manner for hydrogen atoms This expression can be reduced to the Balmer relationship, where is the Rydberg constant and is equivalent to : When a gas is heated, it emits discrete wavelengths that are unique to that element. From these wavelengths therefore, it is possible to identify an unknown gas. In this experiment, the wavelengths will be measured with a diffraction grating spectrometer. For slit images of the first order, they follow the equation, where is the angle measured and d the grating spacing. This experiment aims to investigate how well the visible light wavelengths of hydrogen predicted by the Bohr’s theory agree with experimental values and to find an experimental value for the Rydberg constant. Subsequently, the experiment aims to apply the results to identify two unknown elements by their visible optical spectra. 2 Methodology All parts of the experiment make use of the same diffraction grating spectrometer and similar discharge tubes containing different gases. The telescope and the collimator tube are adjusted before measurements begin so that a sharp image of the slit is obtained when the discharge tube is placed as close to the slit at the end of the collimator as possible. The diffraction grating, for which the exact slit separation d is unknown, is placed in between the collimator and the telescope, such that the grating is perpendicular to the collimator. Once set, the
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Atomic Spectra report - Atomic Spectra Li Cheuk Kwan Jeremy...

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