Light from a lamp, which emits light a several discreet different wavelength, illuminates an 800 line/mm diffraction grating. A screen is placed 50.0 cm behind the grating where the light is observed. Light of wavelength 501.5 nm creates a first-order bring fringe 21.90 cm from the central maximum. (a) what is the wavelength of the first-order bright fringe that is 37.80 cm from the central maximum ? (b) if the screen is very long, what is the maximum number of bright fringes for the light of wavelength 501.5nm ?