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Two slits are made 10 mm apart and the screen is placed 1.5 m away. What is the fringe separation when light of wavelength 7000 A is used?

Asked in GUJCET 2023 · Fringe width and fringe position

Answer: (1) 105 μm

Step-by-step solution

Given: d = 10 mm = 1×10⁻² m, D = 1.5 m, λ = 7000 A = 7×10⁻⁷ m.

Idea: the separation of neighbouring fringes is the fringe width β = (λ D)/d.

β = ((7×10⁻⁷)(1.5))/(1×10⁻²) = (1.05×10⁻⁶)/(1×10⁻²).

β = 1.05×10⁻⁴ m.

Written in micrometres that is 105 μm, about a tenth of a millimetre.

Why the other options are wrong

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