Bored - technical puzzle to solve

[hartech]

This picture is of one of the slats in a window blind in Spain that light shines through when the blind is down.

The slits in the blind are 1mm by 10mm long.

what shape will the image of the light shining through the blind slits be when it hits the wall 12 feet away?

Answers with pictures to follow.

Baz.

[IMI A]

Circles?

i.e. round spots on the wall

Edited by IMI A on Monday 13th April 10:34

[hartech]

This is the result of shining a torch light through the same slit onto a wall - still a slit?

There will be a prize for whoever gets the original question right! (ignore to curve - its the light from the torch over the top of the slat)

Baz

[SCEtoAUX]

hartech said:

This picture is of one of the slats in a window blind in Spain that light shines through when the blind is down.

The slits in the blind are 1mm by 10mm long.

what shape will the image of the light shining through the blind slits be when it hits the wall 12 feet away?

Answers with pictures to follow.

Baz.

Shaped a bit like Lucy Pinder? Guessing for a friend.

[julian64]

It will show a diffraction pattern of multiple horizontal light and dark lines. Its demonstrating the duality of light as a wave and particle

[Wiccan of Darkness]

I reckon it'll look like the very hungry caterpillar, a series of circles joined up.

In reality, the answer will show nothing as the op will forget to disable the flash on the camera.......

[glenrobbo]

I am puzzling over the relevance of the "in Spain" bit.
Does that somehow make a difference to the light pattern?

I would hazard a guess that the projected pattern on the wall is a series of overlapping circles.

[hartech]

The reason Spain was relevant was because I don't have blinds in the UK, the sun rarely is bright enough and I am usually too busy to sit and ponder on the outcome!

I was sat with the blind on my left and the image on my right - and it wasn't a slit! which didn't make a lot of sense - and unusually I had time on my hands to try and explain it.

Baz

[FreeLitres]

julian64 said:

It will show a diffraction pattern of multiple horizontal light and dark lines. Its demonstrating the duality of light as a wave and particle

I don't think this is quite right.

The diffraction pattern occurs through these slits as light is a wave, and it is acting like a wave, as expected.

Particles behaving like waves is a more exciting discovery, where electrons ("particles") were directed through slits and they projected as interference patterns, therefore behaving like waves.

Seeing diffraction patterns from waves through slits is still interesting but doesn't demonstrate anything about wave-particle duality IMO.

[motco]

Diffuse horizontal ellipse

[colin_p]

Rainbows, yay!

Or Schrödinger's cat's shadow.

[julian64]

FreeLitres said:

julian64 said:

It will show a diffraction pattern of multiple horizontal light and dark lines. Its demonstrating the duality of light as a wave and particle

I don't think this is quite right.

The diffraction pattern occurs through these slits as light is a wave, and it is acting like a wave, as expected.

Particles behaving like waves is a more exciting discovery, where electrons ("particles") were directed through slits and they projected as interference patterns, therefore behaving like waves.

Seeing diffraction patterns from waves through slits is still interesting but doesn't demonstrate anything about wave-particle duality IMO.

Okay, light isn't a wave. Its made up of photons, which are particles. The many photons going through the slit should just show a slit on the wall, but they don't. They show an interference pattern that would be expected if light was a wave. Reduce the light passing through the slit down to a single particle at a time and they still show a diffraction pattern. Hence light has properties of a particle and a wave. Its a duality.
Bit difficult to describe in a sentence, but there is a lot online about it.

However the answer to the original question stands

[Getragdogleg]

glenrobbo said:

I am puzzling over the relevance of the "in Spain" bit.
Does that somehow make a difference to the light pattern?

Like all good puzzles the Spain line is a red herring, everyone knows that being in Spain won't affect the light.

Now, if we were being asked about rain and where it falls (mainly) then it would be a good clue.

[hartech]

Having spent most of my adult life solving tangible problems - this beat me - here is the picture of the result downstairs and the same thing upstairs.

How can a slit if thin light re-emerge perfectly round and the same brightness all across the circle?

Some explanations will follow - but what's yours?

Thoroughly enjoyed yours answers bye the way,


Baz

[hartech]

[motco]

Fascinating! I'd like to see what just one slit ends up showing on the wall.

[colin_p]

A very fine mesh grille in said slits.

[hartech]

Each circle is from one of the slits (it is a wide blind with many slats) and each circle is the same distance apart as the slits (both sideways and vertically because I measured it).

It means a thin slit turned into a perfect circle somehow - any ideas?

Baz

[nw942]

I assume it's not the same shape right now

[Jim1064]

You will see an image of the light source - which in this case is the sun - a circle. The slit works a bit like a pinhole camera and the actual shape of the hole is irrelevant. This is only true when the light source and wall are far away from the hole.

This effect is quite remarkable during a partial eclipse of the sun: as the sun shines through the gaps of leaves on a tree, the pattern of light on the ground shows crescents:

https://www.youtube.com/watch?v=i_L1xiy5260

(edited to add link)

Edited by Jim1064 on Monday 13th April 20:29

Edited by Jim1064 on Monday 13th April 21:37