Answer: The midpoint between the two slits on the screen.
- A The midpoint between the two slits on the screen
- B Directly behind the first slit on the screen
- C Directly behind the second slit on the screen
- D At the outer edges of the illuminated screen region
Correct answer: A. The midpoint between the two slits on the screen
Explanation: The central bright fringe (n=0) is at the midpoint where path difference = 0. It is equidistant from both slits.
Two coherent slits S₁ and S₂ act as secondary sources; at each point on the screen, the path difference between light from S₁ and S₂ determines whether the waves arrive in phase (bright fringe) or out of phase (dark fringe), producing the characteristic alternating fringe pattern.
Concept context
Huygens principle, Young's double slit, diffraction, polarization. Essential for JEE.