Yes, even if the slit size is smaller than the wavelength of the light, it will still diffract. Diffraction is a fundamental property of waves, including light waves. It occurs when a wave encounters an obstacle or aperture and bends around it, spreading out and interfering with itself. The amount of diffraction depends on the size of the obstacle or aperture relative to the wavelength of the wave.
When the slit size is smaller than the wavelength of the light, the diffraction effect will still be present, but it may be less pronounced compared to when the slit size is comparable to or larger than the wavelength. In this case, the diffraction pattern will have a narrower angular spread and less pronounced interference fringes.
It's important to note that diffraction is a continuous phenomenon, and it becomes more noticeable as the size of the slit approaches or exceeds the wavelength of the light. However, even with a slit size smaller than the wavelength, there will still be some degree of diffraction occurring.