YDSE Phase Difference and Bright Fringe – Rankers Physics

Young's Double Slit Experiment: Practice Problem & Solution

Assertion (A): In standard YDSE set up with visible light, the position on screen where phase difference is zero appears bright. Reason (R): In YDSE set up amplitude of electromagnetic field at central bright fringe is not varying with time.  
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Young's Double Slit Experiment. Understanding the underlying formula is key to arriving at the correct answer below:

A zero phase difference signifies constructive interference, resulting in a bright fringe. Hence, A is true. The amplitude of the electromagnetic field at the central bright fringe remains constant over time in a stable interference pattern, but this is not the reason for it being bright due to zero phase difference. Hence, R is true but not the correct explanation for A.

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