Answer: Decrease the fringe width.
- A Decrease the fringe width
- B Increase the fringe width
- C Not affect the fringe width
- D Make fringes disappear
Correct answer: A. Decrease the fringe width
Explanation: β = λD/d. Increasing d (denominator) decreases β. The fringes become narrower and closer together.
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.