Two coherent sources of equal intensity I produce a resultant intensity 3I at a point. If the path difference is the least positive value capable of producing this intensity, what is that path difference?
Options

Question

Two coherent sources of equal intensity I produce a resultant intensity 3I at a point. If the path difference is the least positive value capable of producing this intensity, what is that path difference?

Options

G1 Physics · Accepted Answer

For equal individual intensities, I(resultant) = 4I cos²(φ ÷ 2). Given, 3I = 4I cos²(φ ÷ 2). Thus, cos²(φ ÷ 2) = 3 ÷ 4. For the least positive solution, φ = π ÷ 3. Hence, Δ = φλ ÷ (2π) = λ ÷ 6. Correct option: B.