What is the explanation for this diffraction pattern?

• azdavesoul
In summary, the conversation discusses an interesting diffraction pattern produced by a simple home setup using a green laser and two parallel panels to create a .5 mm single slit. By moving one panel closer to the laser while maintaining the .5 mm gap, the pattern changes from narrow to wide bands. However, this is not a new phenomenon and is dependent on the details of the setup and shape of the diffraction. The setup consists of a green LED laser, a paper grid, and two aluminum panels painted black.
azdavesoul

While playing with lasers in a simple home setup, I have produced asymmetrical diffraction patterns and have been unable to locate explanations in the public domain. By using a green led laser and two parallel panels to create a .5 mm single slit I got a normal diffraction pattern. Then moving one panel 1 cm closer to the laser source while maintaining the .5 mm gap, I got a pattern that changed from narrow bands on one side with progressively larger and wider spaced bands on the other extreme.

Is this new and interesting or have multiple physics students been playing with these patterns for years without bothering to publish.

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Sorry, but this is nothing new. You will get a diffraction pattern even from a single edge. The fringe spacing depends on the wavelength and the distance to the screen- which is different for your two edges.

I understand that, what struck me as hard to understand is that the pattern was progressive. It varies from thin to thick. Is this just a example of a ‘wave’ pattern where each band is affected by both edges?

Here is a clearer pattern and the setup I used.

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The pattern will depend, entirely, on the details of the diffracting shape involved. What is the actual shape and setup? (not a picture of the equipment but a diagram of the 'slot' or whatever). Remember, the slot depth is relevant as well as the basic width dimension. The simple formula is for a slot in an infinitely thin sheet. In general, the pattern will never be just symmetrical.

Sophiecentaur,
The light source is a green led laser, 532 nm.
The target is a paper grid, ruled at 1 cm, 5 meters from the slit
The slit consists of two aluminum panels, .2 mm thick, painted flat black, perpendicular to the laser beam.
The panel on the left side is 1 cm closer to the laser.

1. What is diffraction and how does it create a pattern?

Diffraction is the bending of waves around obstacles or through narrow openings. When waves encounter an object or opening that is similar in size to their wavelength, they will diffract and spread out. This results in the creation of a diffraction pattern, which is a series of bright and dark bands that can be seen when the waves are projected onto a surface.

2. Why does the diffraction pattern appear as a series of bright and dark bands?

The bright and dark bands in a diffraction pattern are a result of constructive and destructive interference. When waves diffract around an obstacle or through an opening, they interfere with each other. This interference can either amplify the waves, resulting in bright bands, or cancel them out, resulting in dark bands.

3. How is the diffraction pattern affected by the size of the obstacle or opening?

The size of the obstacle or opening has a direct impact on the diffraction pattern. As the size of the obstacle or opening decreases, the amount of diffraction increases, resulting in a wider and more spread out pattern. Conversely, as the size of the obstacle or opening increases, the amount of diffraction decreases, resulting in a narrower and less spread out pattern.

4. Can the diffraction pattern be used to determine the size of an object or opening?

Yes, the diffraction pattern can be used to determine the size of an object or opening. By analyzing the width and spacing of the diffraction pattern, scientists can calculate the size of the obstacle or opening that caused the diffraction. This is a useful tool in various fields, such as microscopy and astronomy.

5. What other factors can affect the diffraction pattern?

The diffraction pattern can also be affected by the properties of the waves, such as their wavelength and amplitude. Additionally, the distance between the source of the waves and the surface where the pattern is projected can also impact the diffraction pattern. Other factors like the shape and material of the obstacle or opening can also play a role in the diffraction pattern.

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