This demonstration uses the famous Michelson interferometer which is used either for precise distance measurements or the wavelength of the laser. An assembly of optical components including HeNe laser, mirrors and converging lenses is used. The interference pattern is produced by splitting the beam into two paths using a 50:50 beam splitter. The movable mirror is motor controlled and computer interfaced, a source of changing the path length and produce a interference fringes.
With a helium-neon laser, we can demonstrate the diffraction of light from a single slit, double slit pattern or from gratings and surfaces of CD’s. The single and double slits are constructed from breaking apart a razor blade and connecting the broken halves back to back. For the double slit a common pin is inserted inside the gap. The obtained diffraction images can also be analyzed using the famous ImageJ software.
These demonstrations bring home useful concepts of interference, diffraction and the wave nature of electromagnetic radiation.