In a Young double-slit experiment, monochromatic light of wavelength 600 nm illuminates two narrow slits separated by 0.30 mm. If the interference screen is placed 1.5 m away, what is the fringe spacing on the screen?
Answer and explanation
Correct answer: C. 3.0 mm
- Step 1: Fringe spacing formula: w = λ D / d. Step 2. Convert units: λ = 6.0 × 10⁻⁷ m, D = 1.5 m, d = 3.0 × 10⁻⁴ m. Step 3. w = (6.0 × 10⁻⁷ × 1.5) / (3.0 × 10⁻⁴) = 9.0 × 10⁻⁷ / 3.0 × 10⁻⁴ = 3.0 × 10⁻³ m = 3.0 mm. Answer: 3.0 mm. Why not the others: 1.5 mm halves the width; 4.5 mm and 6.0 mm are incorrect multiples.
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