Venue: The University of Melbourne Lecturer: Dr Eddy de Jong

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1 PHYSICS VCE SUMMER SCHOOL 2012 A headstart on VCE Physics Units 3&4 Venue: The University of Melbourne Lecturer: Dr Eddy de Jong Thursday 19 January 10:00 am 3:00 pm and Friday 20 January 10:00 3:00 pm National Educational Advancement Programs (Neap) Pty Ltd ABN Pelham Street Carlton Victoria 3053 Telephone (03) Facsimile (03) This publication is independently produced for students of VCE. Although material may have been reproduced with the permission of the VCAA, the publication is in no way connected to or endorsed by the VCAA. The notes, handouts and other documents issued at lectures have been specifically researched and produced by Neap. Reproduction of the whole or part of any document constitutes an infringement of copyright. None of the material may be used or passed on to other persons without the prior written consent of Neap. Copyright Neap 2012 PHYSICS TITLE.FM

2 Contents Introduction to Physics Units 3& Introduction Structure of the Unit 3 Physics course Structure of the Unit 4 Physics course Numerical questions Multiple-choice questions Explain /extended-answer questions How to succeed in the Physics examinations Electronics and photonics Introduction Input/output transducers Voltage dividers Smart circuits Diodes Photodiodes Voltage amplifiers Light-emitting diodes (LEDs) Motion in one and two dimensions Motion in a straight line Vectors Force Newton s laws of motion Circular motion Projectile motion Impulse and momentum Momentum conservation Energy, work and power Hooke s law Conservation of energy Collisions Gravity Weight, apparent weight and weightlessness Satellites and planetary motion Solutions Electric power Magnetic fields produced by bar magnets The unit of magnetic field strength (tesla) Copyright Neap SUPHYS12TOC.FM 1

3 VCE Physics Units 3&4 Summer School 1.3 Magnetic fields produced by currents The right-hand grip rule The left-hand rule and right-hand slap rule A simple DC motor and the role of the commutator Magnetic flux Induced emf Lenz s law AC generators Properties of AC voltage Transformers Electricity distribution networks Advantages of high-voltage power transmission Interactions of light and matter Models Young s double-slit experiment Interference patterns Diffraction of waves Photoelectric effect and the particle-like nature of light Einstein s explanation of the photoelectric effect The de Broglie wavelength Momentum of photons Electron standing waves Atomic emission spectra Atomic absorption spectra Where do emission and absorption lines come from? Summary Solutions Detailed studies Introduction Einstein s special relativity Materials and their use in structures Further electronics Synchrotron and its applications Photonics Sound Solutions Appendices Appendix A Data sheet for VCE Physics Unit Appendix B Data sheet for VCE Physics Unit Appendix C Common electronic symbols SUPHYS12TOC.FM Copyright Neap

4 VCE Physics Units 3&4 Summer School (1 volt = 1 joule per coulomb of charge) Physical relationships A potential difference results in the flow of current in a wire, as shown in Figure 8. V H, high potential V L, low potential I, current resistive device R Figure 8 V H V L = IR If we apply the same potential difference across two lengths of different wire, different currents will result. This characteristic of a conductor is called the resistance. R = V Ī - (1 ohm = 1 joule per second) Power is the rate of energy dissipated through a resistive element. power = energy dissipated time taken P = U --- t (1 watt = 1 joule per second) (energy dissipated = work done on resistive element = potential difference total charge passing through it) V 2 For all circuits, P = VI= = I 2 R. R (power supplied by battery = sum of individual powers developed in individual resistances) Resistors in series and parallel The formula for resistors in series is R total = R 1 + R 2 + R 3 Figure 9 shows three resistors in series. R 1 R 2 R 3 Figure 9 The current through resistors in series is always constant and is always the same as the current through the battery (as long as the battery does not run down). If the battery runs down (say from 12 V to 10 V) and the resistances stay the same, the current will be less (since V = IR). 14 SUPHYSL1&2_2012.FM Copyright Neap

5 Interactions of light and matter Applications Microscopy Diffraction of the light waves passing through a microscope will limit its resolution and, therefore, its useful magnification. There is no use in making the image larger once the details of the image cannot be resolved. Now the resolution of a microscope is directly proportional to the wavelength of the light used. This means that normal light microscopes have a minimum resolution of about 250 nm and a maximum useful magnification of about 400. However, the de Broglie wavelength of an electron accelerated through a potential difference of 50 kv is only about nm, which suggests that a microscope using electrons instead of light would have a resolution of the same value. In practice, the electrons must be focused by electromagnetic fields which act as lenses, and aberrations in these lenses limit the resolution to about nm. This is still 1000 times better than the best light microscope. Indeed it is comparable to the size of an atom and, under certain conditions, some atoms have been visualised by the electron microscope. An electron of mass kg is travelling at a speed of m s 1. Question 25 Calculate the kinetic energy (in J) of this electron. J Question 26 Calculate the de Broglie wavelength of this electron. m Copyright Neap SUPHYSL3&4_2012.FM 107