1.
In Young's double slit experiment, the slits are 2 mm apart and are illuminated by photons of two wavelengths λ1=12000\lambda_1 = 12000 \AA and λ2=10000\lambda_2 = 10000 \AA. At what minimum distance from the common central bright fringe on the screen 2 m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other?