If the hole is smaller than the wavelength of light, it can have interesting optical effects. In general, when the size of an opening or obstacle becomes comparable to or smaller than the wavelength of light, it can result in phenomena such as diffraction and scattering.
Diffraction is the bending and spreading of light as it passes through an opening or encounters an obstacle. When the size of the hole is smaller than the wavelength of light, diffraction becomes significant, and the light waves spread out and interfere with each other. As a result, the light may be dispersed in various directions, making it challenging to see through the small hole directly. This effect is similar to what happens when light passes through a narrow slit or encounters a sharp edge.
However, the specific details of what you can see, if anything, will depend on the exact size and shape of the hole, as well as the properties of the incident light. Some light may still pass through the hole, but it could be spread out or diffracted to such an extent that the image appears blurry or distorted.
In summary, if the hole is smaller than the wavelength of light, it can result in diffraction and scattering, making it challenging to see through the hole clearly. The details of what can be observed will depend on the specific circumstances.