Question

Difference between first order and second order diffraction

Answer 1

The first bright image to either side occurs when the difference in the pathlength of the light from adjacent slits of the grating is one wavelength, and it is called the "first order"diffraction maximum. ... When light of multiple wavelengths is used, the different wavelengths(different colors) are separated.

Answer 2

Diffraction from a single slit. Young's experiment with finite slits. Diffraction pattern from a single slit. First order minima. Higher order minima. Intensity I(θ) Graphing I(θ) with the phasor sum. Varying the slit width. Young's experiement with finite slit width. Further reading.The single slit. When light passes through a single slit whose width w is on the order of the wavelength of the light, then we can observe a single slit diffraction pattern on a screen that is a distance L >> w away from the slit. The intensity is a function of angle.