When light is constrained to a distance shorter than its wavelength, it can exhibit various phenomena depending on the specific conditions. Here are a few examples:
Diffraction: When light encounters an obstacle or aperture that is comparable in size to its wavelength, it undergoes diffraction. Diffraction causes the light to spread out and bend around the edges of the obstacle, resulting in the phenomenon of interference patterns and the appearance of fringes. This effect is commonly observed with light passing through small slits or diffracting through edges.
Evanescent Waves: In certain situations, when light is incident on an interface between two media at an angle greater than the critical angle, it can produce evanescent waves. These waves propagate along the interface and decay exponentially with distance from the interface. They are considered near-field components and are involved in phenomena such as total internal reflection and the operation of some optical devices like near-field scanning microscopy.
Enhanced Electric Fields: When light interacts with subwavelength structures, such as nanoparticles or nanoscale apertures, the electric field of the light can be significantly enhanced due to constructive interference. This phenomenon is known as localized surface plasmon resonance and finds applications in sensing, imaging, and surface-enhanced spectroscopy.
It's important to note that these effects depend on the specific conditions and geometry involved. The interaction between light and structures shorter than its wavelength can result in unique and interesting phenomena that are utilized in various fields of research and technology.