tink200

hi guys, i have been trying to figure out this question for days now i think its a case of wrong formulas but im not entirly sure, so any help would be gratly appreciated! i have been told that monochromatic light from a laser is directed towards a diffraction grating with 300 lines per millimetre. A diffraction pattern on a screen situated beyond the grating consists of a series of spots of light. The first order spot (d) is situated 2.00m (200mm) from the centre of the grating, at a diffraction angle of 11.8 degrees, assume that the speed of light is 3.0x10^8 m s-1. the questions are......... 1) calculate the distance (s) (in mm) from the centre of the diffraction pattern to the first order spot (i have been using the equation s= din11.8 x d, please correct me if i am wrong) 2)calculate the wavelength of the light of the laser? now this is where i am running into problems i cannot use wavelength=frequency x c because i do not know the frequency, so instead i am using wavelength= sin11.8 x d/s is this correct?? 3) calculate the frequency ...no probs assume it would be f= c/wavelength the prob with the way i am doing it is the colour of the light is supposed to be in the visible part of the spectum, but the best i have come up with so far is 2 values either side of the visible range!!?? all i need is clarification on the formulas i am using, and if i am wrong then a point in the right direction thanx