A Young's double slit apparatus features slits separated by 0.28 mm and a screen located 48 cm from the slits. The entire setup is submerged in water, and the slits are illuminated with red light ( = 700 nm in vacuum). Determine the fringe-width of the pattern produced on the screen.

Step-by-step solution

Given: d = 0.28 mm = 0.28 10⁻³ m D = 48 cm = 0.48 m = 700 nm = 700 10⁻⁹ m The refractive index of water is = 4 3 . The wavelength of light in water is given by: ' = = 700 10⁻⁹ 4 3 = 525 10⁻⁹ m The fringe-width is given by the formula: = ' D d Substituting the values: = 525 10⁻⁹ 0.48 0.28 10⁻³ = 525 10⁻⁶ 48 28 = 525 10⁻⁶ 12 7 = 75 12 10⁻⁶ m = 900 10⁻⁶ m = 0.9 mm