Andre W. answered 12/12/13
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The angle of diffraction is directly related to the wavelength of the wave: longer waves are diffracted (bent around obstacles) more than shorter waves. Among electromagnetic waves, radio waves are diffracted more than visible light, since radio waves have wavelengths of a few meters or kilometers, while light has wavelengths of a few hundred nanometers. Sound waves, which are mechanical waves, generally have longer wavelengths than visible light, which is why we can hear around obstacles but not see around them.