BTEC Applied Science Unit 1: Physics - Wave Interference

Introduction

• Focus on wave interference using coherent sources.
• Comparison of sound from one versus two speakers.

Coherent Sources

• Definition: Two sources emitting waves of the same wavelength, frequency, and amplitude, in phase.
• Example: Two speakers emitting the same note, producing interference patterns.

Superposition Principle

• Concept: When waves from different sources meet, they superimpose.
• Types of Interference:
  • Constructive Interference: Occurs when waves are in phase, resulting in increased amplitude.
  • Destructive Interference: Occurs when waves are in antiphase, leading to cancellation.

Phases of Waves

• In Phase: Waves rise and fall together.
• Antiphase: Waves are opposite; when one rises, the other falls.

Applications

• Sound Waves:
  • Constructive interference results in louder sound.
  • Destructive interference results in quieter sound.
• Water Waves:
  • Demonstration using two point sources creating circular wave fronts.

Path Difference

• Definition: The difference in distance traveled by two waves to a point.
• Influence on Interference:
  • If path difference is a whole number of wavelengths, constructive interference occurs.
  • If path difference is a half wavelength, destructive interference occurs.

Example Analysis

• Point X: Constructive interference due to equal path traveled.
• Point Z: Constructive interference because path difference equals a full wavelength.
• Point Y: Destructive interference due to path difference of half a wavelength.

Conclusion

• Wave interference patterns depend on the coherence of sources and the path difference between them.
• Understanding these principles can predict when and where constructive or destructive interference will occur.