The size of the obstacel in order to observe diffraction fo light must be

The size of obstacle in order to observe diffraction of light must be

Diffraction of light is

What should be the order of the size of an obstacle or aperture to produce diffraction of light?

It is difficult to observe diffraction in case of light because

The correct relation between the size of the obstacle and wavelength of light in order to observe thde diffraction event is