In a double-slit interference experiment, what happens to the fringe spacing on the screen if the slit separation d is decreased?
Answer and explanation
Correct answer: B. Fringe spacing increases
- Step 1: The fringe separation formula is Delta y = (lambda * L) / d.
- Step 2: Since fringe width Delta y is inversely proportional to slit spacing d, decreasing d causes Delta y to increase.
Answer
Fringe spacing increases.
Why not the others: 'Fringe spacing decreases' assumes direct proportionality to slit spacing; 'Fringe spacing remains unchanged' ignores the geometry of the double-slit apparatus; 'Fringes disappear completely' would only occur if coherent illumination is removed.
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