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Major Concepts in Physics Lecture 7. . Prof Simon Catterall Office 309 Physics, x 5978 smc@physics.syr.edu http://physics/courses/PHY102.08Spring. Exam 1. Logistics – Monday 11 th Feb in class. Sample exam, quiz and homework 1 solutions online. Review today and in workshop this week
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Major Concepts in Physics Lecture 7. Prof Simon Catterall Office 309 Physics, x 5978 smc@physics.syr.edu http://physics/courses/PHY102.08Spring PHY102
Exam 1 • Logistics – Monday 11th Feb in class. • Sample exam, quiz and homework 1 solutions online. • Review today and in workshop this week • Seat assignment – outside Stolkin • Formula sheet provided – DO NOT BRING YOUR OWN • 1 of 3 midterms – 2 highest scoring count. PHY102
What should I know ? • Lectures 1—6. Homework 1 and quiz 1 • Workshop material – where it builds on lectures etc • Textbook: • Chapter 11. Chapter 12, sections 12.1, 12.4. Chapter 22., sections 22.1, 22.4 • Chapter 25, sections 25.1, 25.3, 25.4, 25.7 PHY102
Quiz 1 • Problem 1. 5 crests pass pt in 10 secs. • So, each oscillation takes 2 seconds. This is hence the time period T. Frequency f=1/T. Wavelength = v/f=0.25x2=0.5 m Some of you were wrongly graded on this – please see me at end PHY102
Key facts about waves • Know the different types of wave (transverse, longitudinal, travelling, standing) • Know key definitions: wavelength, frequency, speed. Know how to write them in terms of angular frequency and wavenumber • Know form of simple wavefunctions y=Asin(wt-kx) PHY102
Standing waves and resonance • Know how to find fundamental modes for sound waves in pipes and vibrating strings • Know how to take these allowed wavelengths and convert to frequencies using wave speed. • Resonance: if drive system at one of these allowed or natural frequencies – large response PHY102
Superposition • Know how to add waves – constructive and destructive interference • Double slit interference. Know how to use formulae for bright/dark fringes • Small angle approx and linear size of fringes on screen • Thin film interference – qualitative aspects PHY102
Diffraction • Qualitative aspects of diffraction – waves bend around objects when wavelength comparable to object size. • Know Huygens principle – wave at later time formed by adding together wavelets originating from wavefront at earlier time. • Know the single slit condition for dark fringes and how to use it PHY102
Electromagnetic spectrum • Know that light and other parts of EM spectrum composed of oscillating electric and magnetic fields – traveling at speed 3x108 m/s away from accelerating charges • Know what wavelengths correspond to different types of wave – radio waves (1 km),microwaves (10 cm), infrared (1 mm-800 nm), visible light (700-400 nm), UV (300 nm), X-rays (0.001 nm), gamma rays PHY102
Examples – basic waves • Write an equation for a (sine) wave with amplitude 0.120 m, wavelength 0.3 m and wave speed 6.4 m/s travelling in the x-direction PHY102
Examples – interference Light of wavelength 650 nm is incident on two slits. A maximum is seen at angle 4.1o and a minimum at 4.78o. What is the order of the maximum and what is the slit separation ? PHY102
Examples – waves in tube • The length of a pipe closed at one end is L. In the standing wave whose frequency is 3 times the fundamental what is the distance nearest node to the closed end ? PHY102
Examples - diffraction • The central bright fringe in a single slit diffraction pattern from light with wavelength 476 nm is 2.0 cm wide on a screen that is 1.05 m away. How wide is the slit ?. How wide are the first two bright fringes on either side of the central fringe ? PHY102