In: Physics
Single slit interference is confusing. we know that the interference happens between two waves so, what would be the source of two waves in the single slit interference. Well, we also know that every wavefront is a source for secondary wave, so if there is a single hole / slit of width "W" then all the points on the wave falling in that width is a source of secondary waves and these can interfere constructively or destructively .
Now consider the case of double slit interference, in which a parallel beam of incident monochromatic (containing a specific wavelength) light from the left strikes a screen with two slits, S1 and S2 , as below.
With L >> d , that two bright spots would be observed on the right hand screen immediately opposite S1 and S2 . The rest of this screen would be in shadow. What is actually observed on the right hand screen is an "interference pattern" as indicated below,
In both the cases the interference is really difference, in single slit we see fading maxima and minima with increasing y. which in double slit the maxima and minima are of same amplitude throughout.
In our daily lives the phenomenon of light-wave interference with oily or filmy surfaces has the effect of filtering light, and this, thus, has a number of applications in areas relating to optics: sunglasses, lenses for cameras, and visors.