In a double-slit experiment, if the wavelength is doubled and the slit separation is halved, the fringe width becomes
A{'text': '1/4 of original', 'label': 'A'}
B{'text': '4 times original', 'label': 'B'}
C{'text': '2 times original', 'label': 'C'}
D{'text': 'Same as original', 'label': 'D'}
Answer & Solution
Correct answer: B. {'text': '4 times original', 'label': 'B'}
1. β = λD/d. New wavelength = 2λ; new slit separation = d/2.
2. New β = (2λ)D / (d/2) = 4 × (λD/d) = 4β.
3. So the fringe width becomes 4 times the original.
4. Screen distance D was kept unchanged.
_Source: NCERT Class 12 Physics, Ch 10 "Wave Optics", §10.4_
Related questions
Newton originally supported the corpuscular theory of light. The wave theory was strongly In a Young's double-slit experiment, a thin transparent sheet of thickness t and refractivCoherent sources are those that emit waves ofIf polarised light of intensity I passes through a polariser whose axis makes angle θ withAn unpolarised light of intensity I₀ passes through a polariser. The transmitted intensityWhich of the following phenomena is characteristic ONLY of transverse waves and NOT of lonThe polarising angle (Brewster angle) for glass of refractive index 1.5 isThe width of the central maximum in single-slit diffraction on a screen at distance D is