Two coherent light sources each of wavelength λ are separated by a distance 3 λ . The total number of minima formed on line AB which runs from - ∞ to + ∞ is:
Text Solution
Verified by ExpertsThe correct answer is:
C
Lets take any general point S on the line AB.
Clearly: for any position of S on line AB; we have for Δ PQS:
PQ + QS > PS {in any triangle sum of 2 sides is more then the third side}
⇒ PS – QS < 3 λ .
As PS – QS represents the path difference at any point on AB ⇒ it can never be more than 3 λ . Now minimas occur at.
only.
so 3 minimas below R (mid point of AB) and 3 also above R.
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