Waves - Cape Breton – Victoria Regional School Board：波-布雷顿角–维多利亚地区学校董事会.docx

RRHS Physics 11Unit 4 Waves? Jim Burke RRHS Physics 11Table of ContentsModule 4.1 Introduction to Waves44.1.1Wave Properties44.1.2Wave Equation174.1.3Two-dimensional Wave Properties274.1.4Module Summary35Module 4.2 Sound Waves364.2.1Sound Waves364.2.2Air Columns494.2.3Beat Frequency674.2.4Module Summary74Module 4.3 Electromagnetic Waves754.3.1Electromagnetic Waves754.3.2Refraction824.3.3Diffraction and Interference of Light1014.3.4Mirrors and Lenses1154.3.5Module Summary143Module 4.1 Introduction to Waves4.1.1Wave PropertiesWhen you send a wave pulse through a rope or a spring, the rope or spring moves back to its rest position after the wave has passed through it. Only the energy moved down the spring. This energy was produced as a result of the vibration of your hand. If this vibration occurs as a repeated pattern over regular time intervals, it is referred to as periodic motion; similarly, the wave created is referred to as a periodic wave.As was seen in the previous module, objects undergoing periodic motion can be described in terms of their period and frequency. Period, , is the amount of time that it takes to complete one full cycle or vibration. Since period is the time required per cycle, it can be calculated usingWhere is the time interval that it takes to complete cycles.You also learned that frequency, the number of cycles in a time interval, is the inverse of period (). Frequency can therefore be calculated usingRemember that the units of frequency are hertz (Hz), which is .ExampleA child swings back and forth on a swing 15 times in 30.0 s. Determine the frequency and period of the swing.SolutionSince period is the time per cycle,Frequency is the inverse, the number of cycles per secondWave TerminologyA wave is a disturbance that transfers energy. If the source producing this energy is periodic in nature, then the wave will also be periodic in nature. We will therefore often use period and frequency to describe waves.Waves can be broken up into two ca