Wiener's historic experiment on standing wave light waves in 1890 introduced a representative example. The superposition of electromagnetic fields of light in modern optics textbooks. In this research, we simply reproduce Wiener's experiment for classroom demonstration. By using an inexpensive laser pointer as the light source and the weak diffuse reflection of the slightly scratched glass, we display the resident light waves in real time instead of photographic film or fluorescent film. In addition, the coherence setting of the laser pointer can also be studied through simple experiments. With the help of modern technology, we are able to demonstrate the real-time observation of the standing lamp
Wave to greatly improve efficiency and simplicity. We also observed standing waves using diffuse reflection.
First, the spectral characteristics of the laser pointer are analyzed with a spectrometer. The center wavelength and FWHM were measured as 647 nm and ~1.0 nm respectively (Figure 3), which is affected by the resolution of the spectrometer. By carefully aligning the silver mirror and the laser source, we make the incident beam and the reflected beam overlap each other. Observe that the glass slide is kept close to the silver mirror at the beginning. To capture the standing wave generated by the scratched glass plate, we use a CCD camera. When we tried various Laser pointer, we could not observe all these standing waves. This can be through multi-mode operation or frequent mode hopping in the diode laser source. In order to observe standing waves, the laser needs to operate in a single mode for a reasonable duration. Usually, the cavity length pointer of the laser is ∼0.2 mm, which gives a mode spacing of ∼1nm, corresponding to a coherence length of ~0.5 mm. If the spectral width of the laser pointer is less than 1 nm, the laser pointer can work in a single mode. One can select the appropriate coherence length of the laser pointer in our experiment for the standing wave experiment by measuring the spectral width or the spectral width. The edge here is observed at a distance of up to 12 cm (24 cm round trip).