Light and Atoms Test 2020.pdf

Assessment Type 2: Skills and Applications Tasks Light and Atoms 2020 2020 PHYSICS Friday September 11, 2020. Time: 105 minutes Stu...

Assessment Type 2: Skills and Applications Tasks Light and Atoms 2020 2020 PHYSICS Friday September 11, 2020. Time: 105 minutes Student Name: _______________________________________________ Teacher: ____________________________________________________ LIGHT AND ATOMS Approved calculators may be used Instructions to Students 1. The assessment is out of 100 marks. Use this as a guide to answering questions by allocating approximately 1 minute per mark. 2. All answers are to be written in the spaces provided. You may make notes on the scribbling paper, but this will not be assessed. 3. The equation sheet provided may be used, but no other notes are permitted. 4. Marks may be deducted if you do not clearly show all steps in the solution of problems, if you give answers with an inappropriate number of significant figures or with incorrect units, or if you do not define additional symbols. You should use diagrams where appropriate in your answers. 5. Use only black or blue pens for all work other than graphs and diagrams, for which you may use a sharp dark pencil. Page 1 of 16  Represent all numerical answers in scientific notation form with the appropriate units and number of significant figures. (KA4 – 5 marks) 1. Many television signals received in Adelaide are broadcast from transmission towers located at Mt Lofty. One such signal is one of Channel 9’s digital TV bands, which transmits information at a frequency of 191.5 MHz. The signal is produced as a result of an alternating current in horizontal elements of the antenna. a) Determine the wavelength of the electromagnetic waves produced by the transmitting antenna. ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ _________________________________________________________ (KA2 – 2 marks) b) Explain why the elements of a receiving antenna must also be aligned horizontally. ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ _________________________________________________________ (KA1 – 2 marks) Page 2 of 16 2. In 1900, Max Planck proposed that the energy of electromagnetic waves was released in “packets” (later called photons). The energy of each photon is directly related to its frequency, but can also be related to other properties like wavelength and momentum. Determine the energy (in eV) of a photon: a) of wavelength 565 nm. b) produced by a HeNe laser with momentum 1.05 × 10–27 kgms–1. ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ________________________________________________________ (KA2 – 6 marks) Page 3 of 16 3. Light of wavelength 634 nm is emitted from a coherant source, then passes through a double slit to illuminate a screen (as depicted below). Point C depicts the position on the screen of the central maximum. At point P, the path difference between light travelling from the first slit (S1), compared to the second slit (S2) is 951 nm. C P a) State whether light from the two slits will constructively or destructively interfere at point P. Justify your answer. ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ________________________________________________________ (KA1 – 3 marks) b) On the diagram depict the intensity of light along the length of the screen that would form from the interference pattern produced. Use the grid above the screen to assist. (KA1 – 4 marks) Page 4 of 16 c) The interference pattern is analysed and it’s found that the angular separation to the 5th maxima is 1.20°. Determine the distance between the two slits in mm. ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ________________________________________________________ (KA2 – 3 marks) d) Describe how the interference pattern seen on the screen would change if… i) …light of wavelength 480 nm was used. ii) …the screen was moved further from the double slit. iii) …the distance between the two slits was reduced. Justify each answer. ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ________________________________________________________ (KA1 – 6 marks) Page 5 of 16 4. In the photoelectric effect, electrons can be emitted from a metal when illuminated by light of a sufficient frequency, constituting a photoelectric current. a) Describe what is meant by the threshold frequency of a metal. ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ________________________________________________________ (KA1 – 2 marks) b) Explain why electrons will not be emitted if the light illuminating the metal is below the threshold frequency. ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ________________________________________________________ (KA1 – 3 marks) c) Electrons will be emitted with some residual kinetic energy when illuminated with light above the threshold frequency. Explain the difference in the photoelectric current if the intensity of this light is increased. ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ________________________________________________________ (KA1 – 3 marks) Page 6 of 16 d) A metal with a work function of 2.44eV is illuminated with light of a range of frequencies, shown in the table below. Frequency of light Will a photoelectric current be produced? 7.00 × 1014 Hz 6.50 × 1014 Hz 6.10 × 1014 Hz 5.70 × 1014 Hz 5.10 × 1014 Hz i) Complete the table to indicate which of the frequencies will cause a photoelectric current. (IAE3 – 5 marks) ii) Choose one frequency which does cause a photoelectric current. Determine the maximum kinetic energy of emitted electrons. ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ________________________________________________________ (KA2 – 2 marks) Page 7 of 16 5. Consider the diagram below, depicting a simple X-ray tube. a) Choose 2 of the parts labelled (E, H, C, A, B, F, and V). Name these 2 parts and describe their function. _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _____________________________________________________________ (KA1 – 4 marks) b) Use the space below to draw the spectrum of X-rays emitted from a typical tube. (IAE2 – 3 marks) Page 8 of 16 c) Show that the maximum frequency (𝑓max ) of x-rays produced by a tube with a potential difference (Δ𝑉) across the tube is given by the formula: 𝑒∆𝑉 𝑓max = ℎ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _____________________________________________________________ (KA2 – 4 marks) d) Using the equation derived in c), determine the tube potential required to produce x-rays up to frequency of 3.62 × 10$% Hz. _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _____________________________________________________________ (KA2 – 2 marks) e) X-rays can be used to image the internal structure of body parts, for purposes such as diagnosing bone fractures. Explain how the use of x-rays allows for an image to be produced with contrast between bone and other body tissues. _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _____________________________________________________________ (KA1 – 2 marks) Page 9 of 16 6. Consider the energy level diagram of an unknown element and the emission spectra of three possible elements that correspond to the diagram, shown below. a) Justify why the unknown element is not Hydrogen (H). (KA1 – 2 Marks) b) Determine the energy (in eV) of the 548 nm photon associated with the Mercury (Hg) emission spectrum. (KA2 – 3 Marks) c) State which of the remaining possible elements, Mercury or Helium (He), the energy level diagram relates to. Justify your answer. (KA1 – 3 Marks) H Hg He ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ Page 10 of 16 7. In 2007, LeBron James had laser eye surgery to help elevate his game (and results since then speak for themselves). For a laser to work, a “population inversion” must be maintained within a set of atoms comprising the laser medium. (a) Describe what a population inversion is and explain why it is necessary for a laser to amplify a source of light. ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ________________________________________________________ (KA1 – 4 marks) (b) Explain why light produced by a laser is considered to be coherent. ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ________________________________________________________ (KA1 – 2 marks) Page 11 of 16 8. The standard model describes the fundamental particles of the universe. These particles can be categorised depending upon their properties. a) Draw lines to match categories of particles (on the left) to their appropriate descriptions on the right. (KA1 – 4 marks) Fermion Particles that mediate the fundamental forces of nature Quark Particles that make up all hadrons Gauge boson Particles that experience all fundamental forces, expect strong nuclear force Lepton Particles that make up everyday matter b) A Kaon is a meson comprising an up quark and a strange anti-quark. Based upon this information, determine the baryon number, lepton number and charge of a Kaon. ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ________________________________________________________ (KA1 – 3 marks) Page 12 of 16  9. Positron Emission Tomography (PET) is a medical imaging technique often used to diagnose disease. A radioactive tracer containing beta-plus emitting nuclei is introduced into a patient’s body. A proton within such a nucleus transmutes into a neutron (mediated by a W+ boson), emitting a positron and an electron neutrino. The positron then interacts with a nearby electron within the patient’s body, causing both particles to annihilate. Figure 1 – A PET scanner Figure 2 – Quark composition of a proton and a neutron a) Why are protons and neutrons both classified as baryons? ____________________________________________________________________ ________________________________________________________ (KA1/2 – 3 marks) b) The reaction below depicts the beta-plus decay event. Show that charge, lepton number, and baryon number is conserved. u → W ! → d + e+ + ν# ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ________________________________________________________ (KA1/2 – 6 marks) c) The annihilation event produces two photons. Write a reaction to depict this event and show that charge, lepton number, and baryon number is conserved. _____________________________________________________________________ _____________________________________________________________________ ________________________________________________________ (KA1/2 – 3 marks) Page 13 of 16 10. Consider the following information, published in Cosmos Magazine in November 2015: Researchers have used electron microscopy to develop a unique way to build 3-D structures as small as one to two billionths of a metre. The study by scientists at the Department of Energy’s Oak Ridge National Laboratory (ORNL) published an account of their work in the journal Small. They show that scanning transmission electron microscopes can be used for precision sculpting in complex oxide materials as well as imaging. “We can make smaller things with more precise shapes,” said ORNL’s Albina Borisevich, who led the study. “When we exposed the amorphous layer to an electron beam, we seemed to nudge it toward adopting its preferred crystalline state,” she said. “It does that exactly where the electron beam is.” The crystal growth in perfect alignment was responsible for the control researchers could bring to bear on the structures. “We’re using fine control of the beam to build something inside the solid itself,” said ORNL’s Stephen Jesse. “We’re making transformations that are buried deep within the structure. It would be like tunnelling inside a mountain to build a house.” The technique provides single atomic plane precision and could be used in fabricating structures for functional nanoscale devices such as microchips. The perfect crystalline alignment ensures that the same electrical and mechanical properties extend throughout the whole material. The scientists happened upon the method by chance while imaging an imperfectly prepared strontium titanate thin film. The sample, consisting of a crystalline substrate covered by an amorphous layer of the same material, transformed as the electron beam passed through it. Page 14 of 16 Identify one of the key concepts of science as a human endeavour, and discuss how this is illustrated in the example on the previous page. ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ___________________________________________________________ (KA3/4 – 6 marks) Page 15 of 16 Extra Space ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ Page 16 of 16