When considering diffraction effects caused by parallel wave fronts incident on an opening in a barrier, the greatest diffraction effects occur when the wavelength of the wave is similar in size to the opening. This phenomenon is known as the principle of Huygens-Fresnel diffraction.
To elaborate further, when the size of the opening is comparable to the wavelength of the wave, diffraction effects become more significant. This is because the wave encounters obstacles at the opening that disrupt its regular propagation, causing it to bend and spread out.
Therefore, for the greatest diffraction effects, you would want a combination of a wavelength that is similar in size to the opening in the barrier. This scenario maximizes the bending and spreading out of the wave, leading to pronounced diffraction patterns.
