Why Does a Convex Lens Create a Flower-Like Light Pattern?

[swaroop]

I have a long tube (aout 30 cm) with a convex lens of diameter 7.5 cm on the one end and a small hole of diameter 2 cm on the other. When i shine a light through the hole and let it pass through the lens, i get a flowery pattern on the wall, looked very strange to me. There is a maxima in the center as expected, then dark for a little further and then patches of light all around the center that resemble petals.

Why is this pattern formed?
Note: This pattern does not appear to form without an apperture smaller than the lens, like a hole.

 

[dauto]

Seems like some kind of lens flare. Hard to tell. Can you post a picture?

 

[swaroop]

Thanks for replying. Here's the pic:

 

[dauto]

After seeing the picture I still think it is some kind of lens flare.

 

[swaroop]

Thanks, I thought this kind of thing only happened in cameras..

 

[Amzer352]

I'm new to these forums, and so far I find them very intriguing. Anyways, the following is to the best of my knowledge, feel free to correct me where I'm wrong. Cameras work just the same as our eyes do. They capture light at a certain moment to generate an image. Though, cameras have something our eyes don't-- Glass lenses as opposed to our organic lenses. This scenario presents a glass lens similar to that of a camera's external lens, with spacing, as in most professional cameras. Is it so crazy to think, then, that we can reproduce lens flare not with a camera, but with our eyes themselves? I think not, given proper conditions, as provided above.

 

[Drakkith]

I'd guess it's simply light scattering from small irregularities around the hole. An experiment you can do is to try to make the hole as smooth as possible and see what the pattern is.

 

[mogulla]

light passing through a small hole to an big aperture, it gets scattered, a diffraction effect also takes place, by which you cam see the flowery shapes.