When the wavelength of a wave is comparable to the size of the slit, interesting phenomena related to diffraction and interference can occur. Let's consider the case of a wave passing through a single slit, although similar effects can be observed in the context of a double-slit experiment.
If the wavelength of the wave is on the order of the size of the slit, several effects can be observed:
Diffraction: Diffraction is the bending or spreading of waves as they pass through an opening or around obstacles. When the wavelength is comparable to the size of the slit, the wavefronts of the wave can diffract or spread out after passing through the slit. This leads to the wave spreading out and producing a wider pattern on a screen placed behind the slit.
Fresnel Diffraction: Fresnel diffraction refers to the diffraction pattern produced when a wave passes through a slit with a size similar to its wavelength. It exhibits a complex pattern of alternating bright and dark regions on a screen behind the slit. The diffraction pattern is influenced by the shape and size of the slit, as well as the wavelength of the wave.
Smearing of Intensity: When the wavelength of the wave becomes comparable to the size of the slit, the intensity distribution on the screen may become less defined. Instead of distinct bright and dark regions, the pattern may exhibit a more blurred or smeared appearance.
It's important to note that the specific behavior and patterns observed depend on the precise setup and conditions of the experiment, including the properties of the wave (e.g., wavelength, amplitude), the size and shape of the slit, and the distance between the slit and the screen.
Overall, when the wavelength of a wave is similar to the size of the slit, the wave exhibits diffraction effects and produces characteristic patterns that are different from those observed when the wavelength is significantly larger or smaller than the slit size.