Intensity in Single Slit Diffraction
The light sources from A1 and A2 make a dark point at P, where sinq = l / b.
When sinq = 0, the screen in the direction of the incident light is very bright.
When sinq = 1
締 / b, the light can group to 3 parts, A1 to A3 , A3 to A4 , and A4 to A5 . The first and second group will interfere to be dark, where coordinated distance between ( A1 , A3 ) or ( A3 , A4 ) are 締. Only the third group is left and the intensity of bright band is reduced.When sinq = 2
締 / b, only one fifth of light is left and the intensity is reduced more.Interference-Diffraction Pattern of Double Slits
When the two slits are wide enough, the intensity
pattern is a combination of the single-slit diffraction
pattern and the double-slit interference pattern.