Question:
The coherence length of the He-Ne laser beam is 120 cm. Its coherence time in seconds is:
The coherence length of the He-Ne laser beam is 120 cm. Its coherence time in seconds is:
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Use \( t_c = L_c / c \), where \( L_c \) is coherence length and \( c \) is speed of light.
Updated On: May 26, 2025
- \( 4 \times 10^{-1} \)
- \( 4 \times 10^{-3} \)
- \( 4 \times 10^{-5} \)
- \( 4 \times 10^{-9} \)
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The Correct Option is D
Solution and Explanation
Coherence time \( t_c = \frac{L_c}{c} = \frac{1.2 \text{ m}}{3 \times 10^8 \text{ m/s}} = 4 \times 10^{-9} \text{ s} \)
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