# Thin hair diffraction

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

ehild

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
Homework Helper
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

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ehild
Homework Helper
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
Homework Helper
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