Physics - Wave Optics Question with Solution | TestHub

Diffraction is the phenomenon of bending of waves around the corners of an obstacle or aperture.

For diffraction to be noticeable and to form a distinct diffraction pattern, the size of the obstacle or aperture (slit width $a$) must be comparable to the wavelength $\lambda$ of the wave.

If $a>>\lambda$, the bending is negligible and the wave exhibits rectilinear propagation.

If $a<<\lambda$, the slit acts as a point source and the wave spreads out uniformly in all directions without forming a characteristic diffraction pattern.

Therefore, diffraction is noticeable only when $a$ is of the order of $\lambda$.

Answer: $a$ is of the order of $\lambda$