Answer: Decreases by factor n.
- A Decreases by factor n
- B Increases by factor n
- C Remains same
- D Doubles
Correct answer: A. Decreases by factor n
Explanation: In a medium, λ' = λ/n (wavelength decreases). Fringe width β = λ'D/d = λD/(nd). Fringe width decreases by factor n.
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.