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Coherence Length Formula:
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Coherence Length is the distance over which the waves remain coherent and is related to the range of wavelengths present in the beam. It represents the propagation distance over which a wave maintains a specified degree of coherence.
The calculator uses the Coherence Length formula:
Where:
Explanation: The coherence length is inversely proportional to the spectral width of the source. A narrower spectral width results in a longer coherence length.
Details: Coherence length is crucial in various applications including interferometry, holography, fiber optics, and laser technology. It determines the maximum path difference for which interference fringes can be observed.
Tips: Enter wavelength and range of wavelengths in meters. Both values must be positive numbers. The calculator will compute the coherence length based on the provided inputs.
Q1: What factors affect coherence length?
A: Coherence length is primarily determined by the spectral width of the light source. Narrower spectral widths result in longer coherence lengths.
Q2: How is coherence length related to coherence time?
A: Coherence length = speed of light × coherence time. They are directly related through the speed of wave propagation.
Q3: What are typical coherence lengths for different light sources?
A: White light has very short coherence length (~1-2 μm), LEDs have moderate coherence length (~10-100 μm), while lasers can have coherence lengths from centimeters to kilometers.
Q4: Why is coherence length important in interferometry?
A: In interferometry, the path difference between the two arms must be less than the coherence length to observe interference fringes.
Q5: Can coherence length be increased?
A: Yes, by using spectral filters to narrow the bandwidth or by using more monochromatic light sources like single-frequency lasers.