《大学物理》英文课件16 Waves-I教程文件.pptVIP

Waves – I;Waves and Particles;Mechanical waves governed by Newton’s laws, exist only within a material medium Electromagnetic waves governed by Maxwell’s equation, require no material medium, travel through vacuum at the same speed, c = 3x108 m/s Matter Waves associated with fundamental particle governed by Schrodinger’s equation;Transverse and Longitudinal Waves ;The red arrow moves to the right with the wave shape The red-dyed string element moves parallel to the y axis ;Period: T Angular frequency: ω Frequency: f ;The Speed of a Traveling Wave ;Sample Problem – Transverse wave, amplitude, wavelength, period, velocity;Sample Problem – Transverse wave, transverse velocity, transverse acceleration;String’s tension and linear density will determine the speed.;Kinetic Energy: associated with transverse velocity of string element (Max zero) Elastic Potential Energy: with string length change Energy Transport: tension forces continuously do work to transfer energy;The Rate of Energy Transmission ;Overlapping waves algebraically add to produce a resultant wave Overlapping waves do not alter the travel of each other ;Interfere and Interference ; in phase out of phase phase-shifted ;Sample Problem – Interference of two waves, same direction, same amplitude;Nodes: where the string never moves. Antinodes: where the amplitude of the resultant wave is a maximum. Standing wave: the wave pattern do not move left or right. ;Traveling waves y1, y2:;Reflections at a Boundary “hard” reflection - a node at the support “soft” reflection - an antinode at the string end ;Standing Waves and Resonance ;Sample Problem;Homework