Extremely Small Radiation From Atoms, Electrons, and Photons - Assignment Example

Running head Title of work Title Name Name of Instructor Subject Institution Date Experiment one                                          Abstract Atoms forms an important aspect in particles in nature. In an atom, the electrons are found around the nucleus. The electrons are   placed in the orbits possessing energy levels. The electron may gain energy by absorbing energy gotten from the 2nd level to their initial level packets called photons. This makes light to be emitted. When the electrons move to a lower energy level energy is absorbed. A given level of energy level of about10.2eV (Willet, 2005) is required for the electron to be either absorbed or emit light. Franks Hertz experiment tries to find out if atoms emit radiations at discrete frequencies. Introduction The study of spectroscopy of atoms, are seen to emit radiations at discrete frequencies. The energy level equation takes in to account the equation ’E=hV (Born, & Raddif, 1969) where h=planks constant v=frequency. The atomic vapor absorbs radiations at given discrete frequencies. This confers with the energy equation. The energy can be transferred through the inelastic scattering of electrons. (Born, & Raddif, 1969). The experiment finds its way in three possibilities namely; The possibility of exciting atoms given the condition of low energy electron condition, Secondly, energy in the atoms from electrons have discrete values and finally, the final results are in terms with the spectroscopic results. Experimental details The apparatus that aid in this experiment includes; hot filament which act as the cathode that emits electrons, the grid that accelerates the electrons at a known range of potential difference, and, the anode, that collects the electrons. The electron gun is enclosed in a glass that’s evacuated and has mercury filled in it. The tube is first heated to a temperature of about 170 degrees Celsius. The accelerating voltage is increased from the cathode and the grid increased from zero and the observation is made. The tube is set at a grid of a maximum of -45 V whereas the anode is set at 0. 85 v. The filament current is turned on progressively till the current that does not exceed a value of 3nA.The filament current is also set at a value of 0.34 a whereas the current for the ac filament should be less than 0.36A.The anode current mini ma are measured which will aid in the determination of the approximately value of the energy level separation in comparison from the first exited state and the ground state. The schematic diagram of the set up is as shown below Results Table results for the values of cathode potential and anode current. Cathode-grid potential (V) Anode current ( nA) -42 -0.51 -40 -2.6 -38 0.49 -36 -0.35 -34 -0.60 -32 -0.26 -30 -0.54 -28 -0.31 -26 -0.24 -24 -0.34 -22 -0.18 -20 -0.31 -18 -0.19 -16 -0.18 -14 -0.197 -12 -0.16 -10 -0.18 -8 -0.14 -6 -0.14 -4 -0.13 -2 -0.12 0 -0.13     Graph of anode potential vs. grid potential Discussions A significant decrease in electron collector current is observed whenever the potential on the grid is raised by an approximately value of 5V.This indicates that the energy is transmitted from the beam in bundles known as quantum of about 5ev.There is a transition from the excited state from 6s 6p3 p1 to 6s 6s1 s0 ground state. It stipulates that, the electron in the beam excites the mercury atom from ground state to 3p1state which makes it to lose energy of about 4.86eV (Willet, 2005). The approximate value of spacing value is 5.02eV.The known accepted value of electron energy is 4.90 eV (Willet, 2005).The spacing value and the location of the first position potential would aid in getting the contact potential contact potential of about 1.58 v is found with an error of about 0.2%. This indicated that at given energy level, the excitation levels would be twice rather than that of the several different levels will be excited. Experiment two Photo electric effect Abstract    It is the effect whereby, electrons are emitted from a metal surface when a given frequency when light possessing some energy is shown. There have being lots of argument about whether light is considered as a wave or a particle. Both statements may be valid depending on the perspective on which one argues from. If light is considered to be a wave, it should contain some specific amplitude to emit the electrons. In other words, it is dependent on the intensity. The frequency levels do not affect the final results. In the case of a particle, Planck and Einstein experiments indicate that energy is only emitted in small packs known as quanta. The Planck’s constant which 6.6*10-34j.s (Born, & Raddif, 1969). Introduction An illumination of an, ultraviolet radiations, enhances electric discharge between the electrodes. Scientist such as Hallwach and Leweard have proved that, the photocurrent arises from irradiated surfaces leading to the effect known as photoelectric effect. Experiment details various apparatus are used in this experiment. A semi cylindrical photocell that has cathode and anode is used. It is enclosed in a light box that has a source of light and wedge filter. The light source protects the anode from irradiation. The bias voltage is provided by a power supply of ratings 2.2volts and a current of 1.1mA.The voltage is monitored by a digital voltmeter while the photo current is measured by the keithley picoammeter Schematic diagram of the set up The values of photo current and bias volts are noted. This is determined from the set up of the voltages of 22v till the photo current reaches zero. Photocurrent vs. voltage graph is drawn. Different wavelength may be used using medium and stronger values then a graph is plotted for comparison purposes. Results Table of photocurrent and anode bias volt   By keeping λ =550 nm and changing the current through light to = 2.3 A. Table of photocurrent and anode bias volts. Voltage (V) Photocurrent ( nA) 22 123 21 121 20 118 19 119 17 119 15 119 13 118 11 115 9 112 7 108 5 0.99 3 0.89 1 0.65 0 0.19 -0.78 0       By choosing λ =450 nm and the current through light = 1.838 A. Table of photocurrent and anode bias volts.     A graph of photocurrent vs the voltage at a λ of550nm and a current of 1.8A A graph of photo current vs. potential at λ of 550 and a current of 0.83A A graph photo current vs. potential at λ of 550 and a current of 2.3A A graph of photo current vs. potential at λ of 550 and a current of 1.833A Discussions             The quantum physics has it from the wave theory that, the electron would only escape from the surface if the energy absorbed by the electron is sufficient enough .Consequently, when the intensity of light increases the forces on each electron raises. In addition, photoelectric effect is exhibited for all radiations frequencies. In Einstein’s Postulates, electromagnetic radiation are considered to have bundles of energy namely photons. The photons have a speed almost like that of light form the equation E =hv (Serway, 2006) where h is the Planck’s constant whereas v is the frequency. In conclusion the experiment indicates that light exist as a particle and possess some energy. The study of electromagnetic theory is important as it find its application at various cases. It is applied in alarm systems, the cinema films, detection of flaws in the halls and in the control of furnaces. Answer to Questions. There is presence of a knee due to the fact that the photoelectric effect produced at the anode has a short wavelength light quanta. Why the minima is not sharply peaked/ This is because the electrons in the photocathode tube have some energy that will usually widen the work function. Contact potential The average value of spacing peak is about 4.98v with an error of 0.1%. Contact potential is calculated from the difference between the first location of the peak and the spacing value.6.29-4.98=1.37V Atoms can return to ground state by emitting photon.Whats the wave length. Give reasons  Yes. Atoms can return to ground state by emitting photons. This arises because the atoms become excited and are raise to further to a higher energy level. The difference in the energy levels that is exhibited is equated to the wavelength function. The wavelength is of about0.498μm. Experiment two Why photocurrent is not zero at zero bias voltage? This is because of the presence of reverse photo current which flows towards the cathode from the anode. This makes some current to be available even when the voltage potential is zero. Electrons possess some energy that they can be able to move on their own Behaviour of the curve at large positive volts The curve behaves asymptotically. Current does not reach zero values. In addition, when the wavelength increases, values of large knees are observed. Why theories about wave theory and Einstein theory do not hold, It is only assumed that one photon is absorbed by the electron from the irradiation of the photo current. However this is not experimentally true. Influence of background effect The intensity of the light affects the amount of electrons emitted. Different intensity have different amount of emission. How h compares with planks constant The experimental H is slightly less than the expected value by about 3.962%.This arises due to some errors that occur during the experiment and the calibration effect. The expected value of   Planck’s constant is 3.621*10-34Js. (Serway, 2006) is determined from the graph, by getting the gradient of the best line of fit. This gives around 2.9816*10-34.The work function is the y intercept whereas the threshold frequency is the x intercept. Systematic and random errors The experiment is not affected greatly by random errors. This may be due to the uncertainties that could not be explained. It is affected greatly by the systematic errors .This is due to the method of plotting the graph that makes the error to be pronounced.The apparatus could also have the calibration errors. Environmental effects can also lead to these errors. To overcome the errors, a more precise measuring instrument should be used. References Born, M, & Raddif, J. (1969). Atomic physics. Scotland: Blacki &son Ltd Serway, R (2006). College physics. Canada: Brooks cole Willet, E. (2005). Basics of quantum physics. Ney York: Rosen Publishing Group. Read More