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.