Young's double slit experiment edges problem

In summary, the photograph shows the interference pattern of monochromatic light on a double slit, with a clear fringe pattern. The X's mark the locations where the path difference between the light from each slit is two wavelengths. The fringes near the center of the photograph are clearer because the waves are almost completely in phase at that point. There are three maximas between the X's, with the central one being the brightest and the ones on each side having a path difference of one wavelength and twice the wavelength, respectively. The fringes may appear dimmer or fuzzier at the edges, and the number of fringe orders can be counted from the center to one edge.
  • #1
meru
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1. The photograph shows the interference pattern produced when monochromatic light falls on a pair of slits.

I cannot post links yet but the photo is of a typical fringe pattern produced by coherent light waves from a double slit.

Mark with an X on the photograph the fringe or fringes where light from one slit has traveled a distance of two wavelengths further than the light from the other slit.

Explain why the fringes near the centre of the photograph are clearer than those near the edges
of the photograph.


3. The answer was given to me. The X's were above two maximas which were 4 fringe spacings and 3 maximas apart. However, i don't understand why the X's are placed so far apart. I thought they would be 2 fringe spacings away from each other as one fringe spacing = one wavelength path difference. And I also don't know why the fringes are clearer at the centre, is it due to the waves being almost completely inphase there? Can someone please clear this up for me. thank you!
 
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  • #2
There will be 3 maximas between the x's, right? The one in the middle is the brightest because that is where the light from each slit has traveled the same distance. The next maximum on each side will be at the location where the path difference is one wavelength.

So, the second maximum on each side of the central will be the locations where the path difference will be twice the wavelength.

And by the fringes being "clearer at the center," do you mean that they are dimmer at the edges? Or are they fuzzier/longer/less distinct? How many orders of fringes are there (count the center as "zero" and proceed to one edge).
 
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  • #3


I would like to clarify the concepts and principles involved in Young's double slit experiment and the observed interference pattern.

Firstly, the interference pattern seen in the photograph is a result of the superposition of two coherent light waves from the two slits. This pattern is characterized by bright and dark fringes, with the bright fringes representing constructive interference and the dark fringes representing destructive interference.

In this experiment, the distance between the two slits is important as it determines the path difference between the two light waves. The path difference is the difference in distance traveled by the two light waves from the slits to the screen. As the light waves are monochromatic (of a single wavelength), the path difference can be expressed as a multiple of the wavelength.

Now, coming to the placement of the X's on the photograph, the distance between them is not necessarily two fringe spacings. This is because the path difference can be any integer multiple of the wavelength, not just one. In this case, the X's were placed above two maximas that were 4 fringe spacings and 3 maximas apart. This means that the path difference between the two light waves is either 4 or 3 times the wavelength. This is possible because the light waves are not confined to only one wavelength, but have a range of wavelengths (known as the spectral bandwidth).

Furthermore, the fringes are clearer at the center of the photograph because that is where the two light waves are almost completely in phase. This means that the crest of one wave overlaps with the crest of the other, resulting in constructive interference and a bright fringe. As we move away from the center, the path difference between the two waves increases, causing the interference to become less and less constructive, resulting in less defined fringes.

In conclusion, Young's double slit experiment is a fundamental demonstration of the wave nature of light and the interference phenomenon. The placement of the X's and the clarity of the fringes are determined by the distance between the slits, the wavelength of the light, and the path difference between the two light waves.
 

What is Young's double slit experiment?

The Young's double slit experiment is an optical experiment that demonstrates the wave nature of light. It involves shining a monochromatic light through two parallel slits and observing the resulting interference pattern on a screen.

What is the "edges problem" in Young's double slit experiment?

The "edges problem" refers to the observation that the interference pattern produced by the experiment is not uniform at the edges of the screen. This is because the edges of the slits act as secondary sources of light, causing interference with the primary interference pattern.

Why does the "edges problem" occur in Young's double slit experiment?

The "edges problem" occurs because the edges of the slits act as secondary sources of light, producing their own interference pattern that overlaps with the primary interference pattern. This creates regions of constructive and destructive interference, resulting in an uneven interference pattern at the edges of the screen.

How can the "edges problem" be minimized in Young's double slit experiment?

To minimize the "edges problem", the slits can be made narrower and closer together, reducing the amount of light that diffracts around the edges. Additionally, using a single-slit aperture or a diffraction grating can also help to reduce the impact of the edges on the interference pattern.

What are the applications of Young's double slit experiment?

The Young's double slit experiment has applications in various fields such as optics, quantum mechanics, and astronomy. It is used to study the wave nature of light and to measure the wavelength of light sources. It has also been used to demonstrate the principle of superposition and to investigate the behavior of particles at the quantum level.

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