The single slit experiment demonstrates an interesting phenomenon of waves called diffraction.

This page is intended for those already familiar with diffraction and wave particle duality of light. To learn about these in brief I recommend this site: SINGLE SLIT DIFFRACTION.

Here are the basics:

- Light doesn’t necessarily travel in straight lines.
- While propagating (ie travelling) it behaves like a wave and when interacting with other objects (screen for example) it gets localised and behaves like a particle.

I will not explain the mathematical derivations related to this experiment(for eg points of destructive interference and fringe width etc). These can be found on the link mentioned above.

What’s interesting about this experiment is that it once again showed that light behaves like a wave, at a time when most people were convinced that it is indeed a particle (after the photoelectric effect and raman effect).

We are taught in middle school that light ‘follows a rectilinear path’, that light propagates as rays and casts sharp shadows. However, Huygen describes propagation of light as a wave. A source of light emits a wavefront (collection of points in the same phase) and each point on the wavefront acts as a secondary source emitting its own wavelets. The overlapping and superimposing of these secondary wavelets forms the next wavefront and so on.

Recently, I got the chance to perform this experiment in my school. So, here are some of the pictures of the exp.