RP01 - Stationary Waves on a String

• What is a stationary wave?

  A wave that stores but doesn't transfer energy
• How do stationary waves form on a piece of string?

  • Two waves, with the same wavelength but travel in opposite directions, interfere with each other
  • When this occurs, they undergo superposition, and form a stationary wave
• What is a node and how do they occur?

  • Node = a point of zero displacement in a standing wave
  • Nodes occur where two waves that are in anti-phase and destructively interfere, cancelling each other out
• What is an antinode and how do they occur?

  • Antinode: a point of maximum displacement in a standing wave
  • Antinodes occur where two waves that are in phase constructively interfere to form a maximum
• Describe the arrangement of nodes and antinodes when the string is vibrating at its fundamental frequency

  At its fundamental frequency, a standing wave will have one central antinode and a single node at each end
• What piece of apparatus can be used to generate a wave in a piece of string?

  A vibration generator that is driven by a signal generator
• What piece of apparatus can be used to alter the length of a string that is oscillating?

  A triangular prism shaped object can be moved along the length of the string to alter the length of the oscillating region
• Why should the signal generator be operated for several minutes before use?

  The signal generator needs time for the frequency to stabilise
• In this experiment, the string is tied to a clamp stand. To carry out this experiment safely, what must you add to the stand?

  A counterweight or g-clamp should be used to produce a counteracting moment that prevents the stand from toppling over
• How does the length of the string affect the frequency of the first harmonic?

  • There is an inverse relationship between the string length and the frequency of the first harmonic
  • As the string length increases, the frequency decreases
• How does the string's mass per unit length affect the frequency of the first harmonic?

  As the mass per unit length increases, the frequency of the first harmonic decreases
• How does the tension in the string affect the frequency of the first harmonic?

  As the tension in the string increases, the frequency of the first harmonic increases
• How can the tension in a string be varied?

  • The tension in a string can be varied by attaching a mass hanger to the end of it
  • As masses are added to the end of it, the tension will increase