In Young's double-slit experiment, when the distance between the slits is smaller than the wavelength of light, an interference pattern is still observed, but it may appear blurred or less distinct compared to when the slit separation is larger than the wavelength.
The interference pattern in the double-slit experiment arises due to the wave nature of light. When light passes through the two slits, it diffracts and creates two coherent sources of waves that overlap and interfere with each other. This interference leads to the characteristic pattern of bright and dark regions on a screen placed behind the slits.
When the slit separation is smaller than the wavelength of light, the diffraction effects become more significant. The diffracted waves from each slit spread out more widely, resulting in greater overlap and interference. This increased diffraction can lead to the blurring or smearing out of the interference pattern.
In such cases, the individual fringes or bright/dark regions in the pattern may not be as sharp or well-defined as when the slit separation is larger. The overall pattern may appear more washed out or less distinct. This blurring effect arises because the narrower slit separation limits the angular separation of the interfering waves, reducing the spatial resolution of the pattern.
To maximize the visibility and sharpness of the interference pattern in the double-slit experiment, it is generally preferred to have the slit separation larger than the wavelength of light. This allows for better separation of the individual interference fringes and clearer observation of the wave interference phenomenon. However, even when the slit separation is smaller than the wavelength, the interference pattern is still observable, albeit with reduced clarity.