In Young's double slit experiment with monochromatic light of wavelength 600 nm , the distance between the slits is 10⁻³ ~m . For changing the fringe width by 3 10⁻⁵ ~m a) the screen is moved away from the slit by 5 cm . b) the screen is moved 5 cm towards the slits. c) the screen is moved 3 cm towards the slits. d) the screen is moved away from the slits by 3 cm .

Step-by-step solution

The fringe width in Young's double-slit experiment is given by = D d , where = 600 10⁻⁹ m is the wavelength, d = 10⁻³ m is the slit separation, and D is the screen distance. When the screen is moved by D , the change in fringe width becomes = D d = 3 10⁻⁵ m. Solving for D : D = d = (3 10⁻⁵) (10⁻³) 600 10⁻⁹ Simplifying yields D = 3 10⁻⁸ 6 10⁻⁷ = 0.5 10⁻¹ = 0.05 m, or 5 cm. Since D > 0 , the screen is moved away from the slits, matching option (a). The correct choice is C .