Physics · Interference: Young's double-slit experiment and expression for fringe width, coherent sources and sustained interference of light

In a Young's double slit experiment, constructive interference is produced at a

In a Young's double slit experiment, constructive interference is produced at a certain point \( P . \) The intensities of light at \( \boldsymbol{P} \) due to the individual sources are 4 and 9 units. The resultant intensity at point \( \boldsymbol{P} \) will be-

  • A. 13 units
  • B. 25 units
  • C. \( \sqrt{97} \) units
  • D. 5 units

Step-by-step solution

For constructive interference, the phase difference is zero, so the resultant intensity is I = I1 + I2 + 2√(I1 I2) = (√I1 + √I2)^2. With I1 = 4, I2 = 9, √I1 = 2, √I2 = 3, sum = 5, square = 25 units.
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