Diffraction MISSING ORDER When condition for maximum intensity in interference ( double slit) and the condition for minimum intensity in diffraction ( single slit) are simultaneously satisfied then those orders are missing from the spectrum known as missing order. Condition for maximum intensity in diffraction (single slit) Question: Deduce the missing order for a double slit Fraunhofer diffraction, the slit width e= 0.16mm and they are 0.8 mm apart. Ans: m/n= (0.16+0.8)/0.16= 0.96/0.16 m/n= 6 m= 6n Question: What particular spectra would be absent if the transparencies and the opacities of the grating are equal? Ans: a=e(given) (e+a)/e= m/n 2e/e=m/n m=2n Since, n= 1;2;3;..... m= 2;4;6;....... N-Slit Diffraction Fraunhofer Diffraction by N-slits(grating) Grating- A grating in an arrangement of N number of pa