tailieunhanh - SAT II Physics (SN) Episode 2 Part 4

Tham khảo tài liệu 'sat ii physics (sn) episode 2 part 4', ngoại ngữ, ngữ pháp tiếng anh phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | There are two major kinds of waves transverse waves and longitudinal waves. The medium transmitting transverse waves oscillates in a direction perpendicular to the direction the wave is traveling. A good example is waves on water the water oscillates up and down while transmitting a wave horizontally. Other common examples include a wave on a string and electromagnetic waves. By contrast the medium transmitting longitudinal waves oscillates in a direction parallel to the direction the wave is traveling. The most commonly discussed form of longitudinal waves is sound. Transverse Waves Waves on a String Imagine or better yet go grab some twine and set up a length of string stretched between two posts so that it is taut. Each point on the string is just like a mass on a spring its equilibrium position lies on the straight line between the two posts and if it is plucked away from its resting position the string will exert a force to restore its equilibrium position causing periodic oscillations. A string is more complicated than a simple mass on a spring however since the oscillation of each point influences nearby points along the string. Plucking a string at one end causes periodic vibrations that eventually travel down the whole length of the string. Now imagine detaching one end of the string from the pole and connecting it to a mass on a spring which oscillates up and down as in the figure below. The oscillation at one end of the string creates waves that propagate or travel down the length of the string. These are called appropriately traveling waves. Don t let this name confuse you the string itself only moves up and down returning to its starting point once per cycle. The wave travels but the medium the string in this case only oscillates up and down. The speed of a wave depends on the medium through which it is traveling. For a stretched string the wave speed depends on the force of tension exerted by the pole on the string and on the mass density of the .