Double-Slit Experiments: Young, Taylor, Light & Electrons

[zoobyshoe]

Visible light has wavelength of the order of hundreds of nanometers.

This suggests another, probably equally naive, question: do photons have anything that corresponds to width? Are shorter wavelength photons narrower than those with longer wavelengths?

2. You are also dealing with a whole spectrum of wavelenghts, not just a monochromatic source. So even if interference occurs, this will occur in a particular location for a particular wavelength, and most likely it will be wiped out by the non-interfering effects from other wavelengths within the visible spectrum.

This makes perfect sense to me. Just to be certain, let me ask: a given photon can only be interfered with by another photon of the same frequency, and it has to be exactly 180º of of phase, correct?

 

[zoobyshoe]

Oily films get their color from interference (of the reflected [not diffracted])
waves between the oil-water-air interfaces.

Does this mean that the colors which you don't see have been canceled by interference?

 

[ZapperZ]

This suggests another, probably equally naive, question: do photons have anything that corresponds to width? Are shorter wavelength photons narrower than those with longer wavelengths?

I don't know. Photons are not defined by its physical size. The wavelength are typically used as a characteris length. However, it would be wrong of me to say that yes, that's the size of a photon.

This makes perfect sense to me. Just to be certain, let me ask: a given photon can only be interfered with by another photon of the same frequency, and it has to be exactly 180º of of phase, correct?

Since you have started to use the "photon language", here is something you have to make sure you understand.

The interference pattern that you are familar with is the result of the interference of SINGLE photons. In a 2-slit experiment, ONE photon has a superposition of 2 different paths. In classical language, it means that it "interferes" with itself! This is what will result in the beloved interference pattern. 2-photon interference almost never happen. It is a higher order effect, and it also produces a remarkably different type of interference pattern.[1,2]

Thus, you can understand why your question above would sound a bit "strange" within the QM/photon picture.

Zz.

[1] T.B. Pittman et al., PRL v.77, p.1917 (1996).
[2] L. Mandel, Rev. Mod. Phys. v.71, p.274 (1999).

 

[zoobyshoe]

The interference pattern that you are familar with is the result of the interference of SINGLE photons. In a 2-slit experiment, ONE photon has a superposition of 2 different paths. In classical language, it means that it "interferes" with itself! This is what will result in the beloved interference pattern. 2-photon interference almost never happen. It is a higher order effect, and it also produces a remarkably different type of interference pattern.[1,2]

I was going to ask how, with white light, all the different frequency photons would happen to end up with another of the same frequency to cancel out. Your explanation, however, neatly takes care of that problem.

However, your exlanation raises at least two more questions 1.) Do some of the photons somehow reinforce themselves by self interference? And, 2.) What happens to the the ones that cancel themselves out? Where does the energy end up?

Thus, you can understand why your question above would sound a bit "strange" within the QM/photon picture.

Same old problem: people who know enough to ask non-strange question usually don't need to ask at all.

[1] T.B. Pittman et al., PRL v.77, p.1917 (1996).
[2] L. Mandel, Rev. Mod. Phys. v.71, p.274 (1999).

If these are on line in a form I don't have to subscribe to something to read them, I'd be very interested to have a look at them.

 

[Antiphon]

Does this mean that the colors which you don't see have been canceled by interference?

No, it is likely that either the "color" (wavelength) is outside the range of
your vision or is a balence of red green and blue that appears as a shade
of grey.

 

[zoobyshoe]

Feathers get their color by a grating effect which is diffraction because
the geomtrical features of interest are smaller than a wavelength.

Iridescence on Butterfly Wings
Address:http://Newton.ex.ac.uk/research/emag/butterflies/iridesc-text.htm
Yes?