Standing Waves on a String

Introduction

When you shake a string, a pulse travels down its length. When it reaches the end, the pulse can be reflected. A series of regularly occurring pulses will generate traveling waves that, after reflection from the other end, will interfere with the oncoming waves. When the conditions are right, the superposition of these waves traveling in opposite directions can give rise to something known as a “standing wave.” That is, there appear to be stationary waves on the string with some parts of the string hardly moving at all and other regions where the string experiences a large displacement. In this lab you will investigate the various factors that give rise to this phenomenon.

Objectives

In this experiment, you will

• Adjust the frequency of the driver so that the string vibrates in the fundamental mode.
• Set up other standing wave patterns on the string.
• Relate the frequency of the various harmonics to that of the fundamental mode of vibration.
• Describe the terms amplitude, frequency, wavelength, node, and antinode as they relate to vibrating strings.
• Determine the velocity of waves in the string.
• Relate wave velocity to the tension of the string and its linear density.