The phenomenon of diffraction occurs when a wave encounters an obstacle or passes through an opening that is comparable in size to its wavelength. When the obstacle or opening is of similar dimensions to the wavelength, diffraction effects become significant. However, if the obstacle is much smaller than the wavelength, the effects of diffraction are minimized or negligible.
To understand why this happens, we need to consider the behavior of waves when they encounter obstacles. When a wave encounters an obstacle or a narrow opening, it spreads out and bends around the edges of the obstacle. This spreading out of the wave is known as diffraction.
The extent of diffraction is determined by the relationship between the wavelength of the wave and the size of the obstacle or opening. If the obstacle is much larger than the wavelength, the wave will not be significantly affected by it, and diffraction effects will be minimal. The wave can simply pass around the obstacle without much disturbance.
On the other hand, when the obstacle or opening is on the order of the wavelength, the wave experiences significant diffraction. The wavefronts bend and spread out, creating a pattern of interference and producing characteristic diffraction patterns. This phenomenon is observed with various waves, including sound waves, water waves, and electromagnetic waves such as light.
When the size of the obstacle or opening becomes much smaller than the wavelength, the wave behaves more like a straight line. The wave essentially "sees" the obstacle as a point source and does not significantly bend or diffract around it. In this case, the wave tends to travel in a straight path with little deviation from its original direction.
In summary, the effect of diffraction is most pronounced when the obstacle or opening is on the order of the wavelength of the wave. This is because waves tend to spread out and bend around obstacles of comparable size, leading to significant diffraction patterns. When the obstacle is much smaller than the wavelength, the diffraction effects are minimized or negligible, and the wave behaves more like a straight line.