1Instructor: Melvin Okamuraemail: [email protected] 1CWaves, optics and modern physicsCourse InformationCourse Syllabus on the web page http://physics.ucsd.edu/students/courses/winter2008/physics1cInstructor: Mel Okamura – [email protected]: 1218 Mayer HallOffice Hrs. Wed , Thu 2-3 pm or by appointmentTA: Margaret Stewart, [email protected],Office: TBAOffice Hrs: TBAText. Physics 1 Serway and Faughn, 7thedition, UCSD custom edition.Class Schedule• Lectures– Mon. Wed. Fri. 12:00-12:50 pm WLH 2005• Quizzes– Alternate Fri. (Starting the 3rdFriday)– 12:00-12:50 pm WLH 2005• Problem Session–TBAGrades• Bi-weekly quizzes (4) will be held on Friday. You are allowed to drop 1 quizzes. There will be no make-up quizzes.• Final exam covering the whole course.• The final grade will be based onQuizzes 60% (best 3 out of 4 quizzes)Final exam 40% Extra credit 5% (clicker responses)Homework• Homework will be assigned each week.• Homework will not be corrected but quiz questions will resemble the homework.• Solutions to the homework problems will be posted on the web page.ClickersInterwrite Personal Response System (PRS) Available at the bookstoreClicker questions will be asked during class. Studentresponses will be recorded. 2 points for each correct answer1 point for each incorrect answer.The clicker points (up to 5% ) will be added to your score at the end of the quarter2Outline• weeks 1-2 Oscillations and Waves• weeks 3-5 Optics• weeks 6 Physical Optics • weeks 7-10 Modern Physics 1.1 Oscillations• Kinematics - sinusoidal waves• Dynamics -Newton’s law and Hooke’s law.• Energetics – Conservation of Energy• Mass on a spring• PendulumOscillations• repetitive displacements with a time period• provide the basis for measuring time• serve as the starting point for describing wave motion.• Example- Mass on a springMass on a springHooke’s Law -Force exerted by spring is proportional to the displacement from the equilibrium position.Fkx=−GGk - Force constant Units N/mHooke’s LawForcedisplacementslope =kF= kx(magnitudes)Vertical directionThe force of gravity is cancelled by the force of the spring.EquilibriumpositionThe force on the object when it is displaced upwardby a distance y from the equilibrium position is only due to the spring.yFky=−JJGGyF3DemoOscillations of mass on a spring.How does the displacement vary with time?Period , FrequencyA -AmplitudeT=Period (s)1fT== Frequency , cycles/s (Hz)ω = 2πf = Angular Frequency (radians /s)Key ConceptsDisplacementTimeTThe oscillation follows a sinusoidal functionThe projection of the rotating vector A on the x axis gives2x Acos( t) Acos(2 ft) Acos( t)Tπ==π=ωθ is the phase anglef is the frequency (cycles/s)ω is the angular frequency (radians/s)displacement, velocity accelerationdxvAsin(t)dt==−ω ω2dva Acos( t)dt==−ω ωx Acos( t)=ωx, v and a are sinusoidal functions with different initialphase angles.The magnitudes of v and a are multiplied by ω or ω2 topreserve the units.DynamicsFmaxFmaxFmaxF=0F=0Newton’s Law applied to mass on springsFma=JGGsFkxkAcost=−=− ω2ma m Acos t=−ω ωkmω=aGmT2k=π1kf2m=πgives4DemoHow does the period of oscillation depend on mass, on the force constant?Calculate the period for the mass spring system.EnergyEnergy required to stretch (compress) a spring bya displacement x21Ekx2=FxWork = FaveragexFaverage=½ kxNote the energy depends on x2so it is independent ofthe sign of x, i.e. same for compression and stretch.FConservation of EnergyStretched springReleased What is the kinetic energy at x=0 ?What is the potential energy at x=0?21KE kA2=PE 0=PEmaxKEmaxPEmaxKEmaxOscillation between KE and PEmax maxPE KE=⇒maxkvAAm==ωFind an expression for the maximum velocity.22max11kA mv22=PendulumThe restoring force is proportional to the displacementfor small displacements.Fmgsin=− θFmg=− θfor small θmgFsL=−Equivalent to Hookes Law with k=mg/LgLω=The period is dependent on Lbut independent of mLT2g=πthen becomeskmω=DemoPendulum oscillations.How does the period depend on L?How does the period depend on