3.5 Coherence

• Coherence is a property of waves that describes how consistent the wave's phase is over time and space
• What is the phase difference in coherent waves?

  Constant
• Temporally coherent waves maintain a constant phase difference over time
• Coherent waves maintain a constant phase difference, which allows them to constructively and destructively interfere to create distinct interference patterns
• Match the type of coherence with its description:

  Spatial Coherence ↔️ Consistency of phase across the wavefront

  Temporal Coherence ↔️ Consistency of phase over time
• What is an application of coherent light in holography?

  Create 3D images
• Why do coherent sources produce sharper diffraction patterns compared to incoherent sources?

  Constant phase difference
• Coherent waves maintain a constant phase difference over time and space.

  True
• Temporal coherence describes the consistency of a wave's phase over time
• Match the application with the source type:

  Holography ↔️ Coherent sources

  White light sources ↔️ Incoherent sources
• Lasers are an example of a coherent source because they exhibit both spatial and temporal coherence
• Match the wave property with its description:

  Coherence ↔️ Consistency of wave phase over time and space

  Constant phase difference ↔️ Allows constructive and destructive interference
• Arrange the following steps in the correct order to describe the behavior of two coherent laser beams:

  1️⃣ Two laser beams with the same frequency and constant phase difference

  2️⃣ Beams interfere constructively and destructively

  3️⃣ Create clear interference fringes
• What frequency condition is required for temporal coherence?

  Constant, single frequency
• What is a common application of incoherent waves?

  White light sources
• For spatial coherence, waves must originate from a single point source or have a constant phase difference across the wavefront
• Match the source type with the diffraction pattern it produces:

  Coherent Source ↔️ Distinct interference patterns

  Incoherent Source ↔️ No discernible interference patterns
• The coherence of the wave source determines the sharpness and distinctness of the diffraction patterns
• What are the two main types of coherence?

  Spatial and temporal
• For temporal coherence, waves must have a constant, single frequency.

  True
• The coherence of a wave source is crucial for the sharpness of diffraction patterns.

  True
• Spatial and temporal coherence are the two main types of coherence


  True
• Incoherent waves do not produce discernible interference patterns
• For spatial coherence, waves must originate from a single point source or have a constant phase difference across the wavefront


  True
• Coherent waves have a constant phase difference, while incoherent waves have a random phase difference


  True
• Spatial and temporal coherence are both necessary for creating distinct interference patterns


  True
• Coherent laser beams can be tightly focused for precise material processing
• What is diffraction in wave phenomena?

  The bending of waves
• Match the wave type with its phase difference:

  Coherent waves ↔️ Constant phase difference

  Incoherent waves ↔️ Random phase difference
• Conditions for coherence in waves:

  1️⃣ Waves must originate from a single point source or have a constant phase difference across the wavefront

  2️⃣ Waves must have the same frequency

  3️⃣ Waves must maintain a constant phase difference over time
• What is one key property of lasers that makes them suitable for optical communication?

  Coherent light beams