1. The problem statement, all variables and given/known data In a Young's double slit experiment , blue monochromatic light of wavelength 450nm is used to illuminate the slits which are 0.60mm apart. A screen is placed 1.5m form the slit is used to catch the interfrence pattern . If red light is used (700nm) , how many red light will be seen? the ans is 7 2. Relevant equations 3. The attempt at a solution dsinθ = m λ 0.6x10^-3 ( sin 90 ) = m (700x10^-9) m = 857 no fringe can be seen = 857+ 857+1 .. What's wrong with my working?