Why does thin hair create a horizontal diffraction pattern?

[okgo]

So I understand that thin hair or wire can make a diffraction pattern, but why would the diffraction pattern be horizontal when the hair is vertical?

 

[ehild]

The pattern consists of vertical dark and bright lines arranged horizontally. Do you know how and why the diffraction pattern is formed?

ehild

 

[okgo]

I believe so. The wavelets due to huygen's principle can still propagate at the edges of the hair. Do the wavelets propagate horizontally around the vertical hair? It just confuses because single slit oriented vertically produce vertical patterns. But hair doesn't and I am told it acts similar to a single slit.

 

[ehild]

Yes, the wavelets starts to propagate at every possible directions at the edges of the hair. The picture shows the hair and wavelets from above.
If you use a laser light, its image is dot-like on the screen, and all diffracted images are dot-like so the pattern is a horizontal arrangement of dots. If the light source is a vertical filament or a slit illuminated with an extended source, the pattern consist of vertical lines.

ehild

 

[okgo]

I'm still a bit confused as to why the dot like patterns are horizontal. What is the black dot? Is that suppose to indicate a circular single slit?

In the following picture, I'm confused as to how the picture on the left translate to the one on the right. As the diffraction pattern on the left is vertical?

http://www.screencast.com/users/trinhn812/folders/Jing/media/f8f8251b-5a86-4deb-bde2-335702fbd1dd

 

[ehild]

The black dot is the cross-section of hair, as seen from vertically above.

The left hand picture in your atatchment is misleading. It shows the vertical hair from the side, but the diffraction pattern is horizontal on the screen, as it is shown in the right-hand picture.

Note that light is diffracted from those places of the surface of an object where the radius of curvature is in the range or less than the wavelength.

ehild

 

[ehild]

The black dot is the cross-section of hair, as seen from vertically above.

The left hand picture in your atatchment is misleading. It shows the vertical hair from the side, but the diffraction pattern is horizontal on the screen, as it is shown in the right-hand picture.

Note that light is diffracted from those places of the surface of an object where the radius of curvature is in the range or less than the wavelength.

ehild