Solve the following questions:

a) Yellow light of 610 nm wavelength passes through a double slit and 5.00 m away on a screen 18 bright interference bands are formed spanning a distance of 18.0 cm. Calculate the distance between the two slits.

b)At what angle would the four maximum from the center in diffraction pattern occur if red light ( = 680 nm) is used ? The slit is 0.0450 mm wide and is 12.0 m from the screen.