Standing Waves

# Standing Waves - PHYSICS 215 STANDING WAVES Object The...

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1 PHYSICS 215 STANDING WAVES Object: The object of this experiment is to study standing waves of two types: 1) transverse waves in a string and 2) sound waves in a tube. The wavelengths of the standing waves will be measured and the velocities of the waves determined. Apparatus: Pasco Interface DataStudio Power Amplifier 1.0 kg or .90 kg mass Mechanical Oscillator String Weighed sample of string Resonance Tube Thermometer 1.0 Introduction The world is full of waves: sound waves, waves on a string, seismic waves, and electromagnetic waves, such as visible light, radio waves, television signals, and x-rays. Sound waves, waves and string, and seismic waves all have as their source a vibrating object, so we can apply the concepts of simple harmonic motion in describing them. In the case of sound waves, the vibrations that produce waves arise from sources such as a person’s vocal chords or a plucked guitar string. The vibration of electrons in an antenna produces a wave on a string. Certain concepts are common to all waves, regardless to their nature. 2.0 Theory 2.1 Types of Waves There are three main types of waves and they are: 1. Mechanical waves. These waves are most familiar because we encounter them almost constantly; common examples include water waves, sound waves, and seismic waves. All these waves have two central features: they are governed by Newton’s laws, and they can exist only within a material medium such as water, air, and rock. 2. Electromagnetic waves. These waves are less familiar, but you use them constantly; common examples include visible and ultraviolet light, radio and television waves, microwaves, x rays, and radar waves. These waves require no material medium to exist. Light waves, for example, travel through the vacuum of space to reach us. All electromagnetic waves traveling through a vacuum have a speed of c = 299 792 458 m/s. 3. Matter waves. Although these waves are commonly used in modern technology, they are probably unfamiliar to you. These waves are associated with electrons, protons, and other fundamental particles, even atoms and molecules. Because we commonly think of these particles as constituting mater, such waves are called matter waves. 2.1 Transverse and Longitudinal Waves A wave sent along a stretched, taut string is the simplest mechanical wave. If you give one end of a stretched string a single up-and-down jerk, a wave in the form of a single pulse travels along the string. This pulse and its motion can occur because the string is under tension. When you pull your end of the string upward, it begins to pull upward on the adjacent section of the string via tension between the two sections. As the adjacent section moves upward, it begins to pull the next section upward, and so on. Meanwhile, you pul down on your end of the string. As each section moves upward in turn, it begins to be pulled back downward by neighboring sections that are already on the way down. The net result is that a distortion in the string’s shape (the pulse) moves along the string at some velocity v.

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