Standing Waves

 

Standing Waves

 

Standing waves is one of the most difficult topics in JEE Physics syllabus. Students find it difficult mainly because it is not very intuitive as compared to other topics. Moreover, the chapter on waves and sound is in general a bit difficult because it is an advanced topic. We will describe this article in points to enhance readablity

 

1.    Understand how standing waves are produced - When two progressive waves of same amplitude and wavelength travelling along a straight line in opposite directions superimpose on each other, stationary waves are formed.
2.    Understand what nodes and antinodes are - The points where displacement is zero are called nodes and the points where the displacement is maximum are called antinodes.
3.    Understand the properties of nodes and antinodes – At nodes, pressure changes are maximum. While, at antinodes, pressure changes are minimum. All the particles (except those that are situated at nodes) execute a simple harmonic motion.
4.    Understand the properties of standing wave as a whole – No energy is transferred in a standing wave. The distance between 2 adjancent nodes is half of the wavelength. This is same as the distance between 2 adjacent antinodes. The particles at nodes are stationary. The particles at antinodes move with maximum velocity. All those particles which are between 2 consecutive nodes vibrate in same phase. A section of wave between 2 adjacent nodes is called as a segment of the wave. The particles in adjacent segments vibrate in opposite phase.
5.    Understand the modes of vibration of a stretched string – This is the most important concept in this chapter and most problems of standing waves are asked from this topic. Students should properly understand fundamental frequenct, first overtone, second overtone, etc. Students should also understand the difference between an overtone and a harmonic. Moreover, students should properly memorize the formulae of frequency in various cases – organ pipe open ended and closed ended. Direct questions are asked in JEE from these formulae and keeping them in memory saves a lot of time.
6.    Understand the concept of end correction – end correction is some times asked in JEE Advanced in error analysis problems. Students should be familiar with it because it is clearly described in NCERT Physics text book and so, not only is it important for JEE Main, but also it is important for JEE Advanced.

 

At last, we would like to mention that students should give a thorough reading of Resnick Halliday Walker by Wiley Publishers. They should also solve the end chapter problems given in the book. This will not only make the subject interesting, but also students will build strong fundamentals as engineering students. Make sure to practice ample of problems from other sources you know. Remember, practice is the key, practice makes a human perfect.

 

We hope the article helped you. Feel free to ask doubts in comments

 

 

About the Author

 

Aman Goel IIT B2 Aman Goel is B.Tech, computer science and engineering undergraduate student at Indian Institute of Technology, Bombay. Born in a business oriented family of Kanpur he secured an All India Rank 33 in JEE advanced 2013 and also scored 323/360 in JEE main 2013. He has also cleared Indian National Physics and Chemistry Olympiads, and KVPY. In his free time, he likes to write articles related to JEE preparation. He loves speedcubing (the art of speed solving a Rubik's cube) and also loves to play computer/mobile games.


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