Measuring Waves in Solids - Required Practical Part 2

Introduction

• Topic: Measuring wavelength, frequency, and speed of waves in a solid.
• Context: Part of a series on waves, building on previous video about water waves.

Apparatus for Measuring Waves in a Solid

• Components:
  • String attached to a vibration generator.
  • Hanging mass to keep the string taut.
  • Signal generator to control frequency.
• Purpose:
  • Measure features of waves in a solid.

Understanding Standing Waves

• Standing Wave: Formed at a certain frequency due to resonance.
• Example: Found in stringed musical instruments like guitars.
• Note: Explanation of standing waves and resonance is not required for exams.

Measuring Wavelength

• Tools Used: Ruler for measuring length of standing wave.
• Procedure:
  • Measure from wooden bridge to vibration generator.
  • Example measurement: 21.5 cm (0.215 meters).

Calculating Wave Speed

• Wave Equation:
  • Wave speed = Frequency x Wavelength
• Example Calculation:
  • Frequency: 10 Hertz
  • Wavelength: 0.215 meters
  • Wave speed = 10 Hz x 0.215 m = 2.15 m/s

Effect of Changing Frequency

• Increasing frequency alters the standing wave.
• Example:
  • With three half wavelengths, measure total length and divide by number of half wavelengths, then multiply by 2.
  • Example calculation:
    • Length = 0.215 meters
    • Wavelength = (0.215 m / 3) x 2 = 0.143 meters
• Frequency for Example: 15 Hertz
• Wave speed Calculation:
  • Wave speed = 15 Hz x 0.143 m = 2.15 m/s

Key Observations

• Wave speed is independent of frequency and wavelength.
• Depends on string tautness and mass per centimeter.

Exam Preparation

• Expect questions on calculating wavelengths from standing waves.
• Method: Divide total length by number of half wavelengths, multiply by 2.
• Resources: Vision workbook contains additional practice questions.