Why do we see diffraction effects in radio waves but not in visible light?

[aaaa202]

When you shine light on a mirror perpendicularly. Does the reflected beam then not interfere with the incoming one? With my intuition it would, and the interference would oscillate between destructive and constructive interference. But then why don't I see that when I do the experiment?

 

[jtbell]

What is the time-scale of such oscillations? Do you have apparatus that can reveal changes on such a time-scale?

Or if you're thinking of spatial separation between maxima and minima, what sort of distances would be involved?

 

[sophiecentaur]

When you shine light on a mirror perpendicularly. Does the reflected beam then not interfere with the incoming one? With my intuition it would, and the interference would oscillate between destructive and constructive interference. But then why don't I see that when I do the experiment?

If you point a beam of radio waves at a reflecting metal plate you do get a standing wave pattern that you can measure easily. Because the wavelength of visible light is so short, you have to go to some trouble to observe obvious diffraction effects.

The coloured reflections from thin oil films on water puddles are due to interference. They form because the oil film is only around i wavelength thick and light is reflected both from air/oil and oil/water interfaces. (Google Thin Film Interference for some nice diagrams).