The Young's double slit exp. and some general waves

In summary, the experiment is designed to determine the nature of light waves, and how they propagate. The light that emerges from the original source is broken down into its primary and secondary waves. The secondary wavelets form at the 2 following slits, and from here on, books continue explaining things but I shall stop here for I have some questions.Q1 - The secondary wavelets do not form only at the slit, but they form everywhere. Why do we consider the secondary wavelets only formed at the slit? Why not in front of it? Why not behind it?The secondary wavelets only form at the slit because that is where the light is focused. The reason for why we consider the secondary wavelets only formed at the
  • #1
WiFO215
420
1
I was reading about the classic Young's double slit experiment and I had a few questions regarding secondary wavelets a.k.a Huygen's wavelets. I proceed with the following questions assuming you know the experiment.

The crucial point behind the explanation to the experiment is that light emerging from the original source, forms secondary wavelets at the 2 following slits. And from here on, books continue explaining things but I shall stop here for I have some questions.

Q1 - The secondary wavelets do not form only at the slit, but they form everywhere. Why do we consider the secondary wavelets only formed at the slit? Why not in front of it? Why not behind it?

Q2 - From the definition of secondary wavelets, I do not understand why nobody seems to discuss why they do produce a 'backlash' effect. Shouldn't the secondary wavelets travel backwards to affect the source itself and cause trouble?

The books I have come across seem to skip discussing these issues. Is there something I have not understood?
 
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  • #2
My understanding is that the "backlashes" of the secondary wavelets interfere with each other and with the original wavelet, so that normally all you see is a single wave propagating outwards from the source. However, when the light passes through a slit, most of the wavelets generated before the slit get blocked by the wall; it's only those wavelets which are centered in the slit itself that can propagate through. And if the slit is thin enough, it looks like just a single wavelet at each slit.

I wouldn't take the Huygens wavelet interpretation too literally, though... it's a nice way to intuitively figure out what happens at something like a slit, but verifying the details gets extremely complicated.
 
  • #3
anirudh215 said:
Q2 - From the definition of secondary wavelets, I do not understand why nobody seems to discuss why they do produce a 'backlash' effect. Shouldn't the secondary wavelets travel backwards to affect the source itself and cause trouble?
Read what I wrote about the obliquity factor in this thread: https://www.physicsforums.com/showthread.php?t=236864
 
  • #4
Thanks Doc!
 

1. What is the Young's double slit experiment?

The Young's double slit experiment is a classic experiment in physics that demonstrates the wave-like nature of light. It involves passing a beam of light through two narrow slits and observing the interference pattern created on a screen behind the slits.

2. What is the purpose of the Young's double slit experiment?

The purpose of the experiment is to demonstrate the wave-like behavior of light and to support the wave theory of light proposed by Thomas Young in the early 1800s. It also helps to understand the principles of interference and diffraction in waves.

3. Can the Young's double slit experiment be performed with other types of waves?

Yes, the experiment can be performed with any type of wave, such as sound waves or water waves. However, it is most commonly performed with light waves due to their small wavelength and ease of manipulation.

4. What are some real-world applications of the Young's double slit experiment?

The experiment has many practical applications, such as in the development of optical instruments like microscopes and telescopes, in the study of diffraction and interference phenomena, and in the production of holograms.

5. Are there any limitations to the Young's double slit experiment?

One limitation is that the experiment assumes the slits are infinitely narrow, which is not possible in real life. Additionally, the experiment can only be used to study waves with a small wavelength, such as light, and cannot be applied to larger objects. Lastly, the experiment does not take into account the quantum nature of light, which is described by both wave and particle properties.

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