Replicating the double-slit experiment at home using a flashlight and a homemade double slit may not produce the expected interference pattern due to several reasons:
Wavelength of light: The wavelength of light emitted by a typical flashlight is relatively large (on the order of hundreds of nanometers for visible light). In order to observe a noticeable interference pattern, the slit separation should be comparable to or smaller than the wavelength of the light being used. A homemade double slit might have a relatively large separation compared to the wavelength of light, resulting in minimal or no observable interference.
Coherence of light: In the double-slit experiment, it is crucial that the light used is coherent, meaning that the light waves have a constant phase relationship. Most flashlights emit incoherent light, where the phases of the waves are random and uncorrelated. Incoherent light does not exhibit the necessary interference properties to generate a clear interference pattern.
Diffraction effects: Even if a double slit with appropriate separation and coherent light is used, achieving a precise double-slit setup at home can be challenging. The size and alignment of the slits, as well as the distance to the screen, need to be carefully controlled to observe distinct interference fringes. Any deviations in these parameters can result in diffraction effects that blur or wash out the interference pattern.
Sensitivity of detection: Capturing the interference pattern typically requires a sensitive detector, such as a photographic plate or a specialized screen designed to detect low-intensity light patterns. Regular screens or cameras may not be sensitive enough to accurately capture the interference pattern.
While it may be challenging to replicate the double-slit experiment at home with readily available materials, there are educational kits or specialized setups designed for this purpose that provide a controlled environment to observe the interference pattern. These setups often utilize lasers or other coherent light sources with precise double slits and screens optimized for interference observations.