Rolling shutter effect on a propeller
When modern digital cameras with an array like sensor capture an image, the color information is mostly saved one line after each other. This means that there is a small amount of time between two consecutively scanned lines of an single image. Imagine a fast moving object like the propeller of an aircraft beeing in the cameras field of view. What happens!? While the scanning line is moving in some direction (e.g. left->right or up->down) the object moves and its shape will get distorted in the final image. You can find dozends of examples on the internet - just type "rolling shutter propeller" in your favourite search engine or click on the first link  below this text. Inspired from an article by Jason Cole which can be found in Link Nr.  or  I tried to recreate this phenomenon using intersection of lines and some other GeoGebra features. What you can see below is a parametric and completely interactive visualization of this "rolling shutter" effect, applied for a propeller with varying number of stick-like "blades". You can vary every parameter and try to understand how it influences the final image. When you've done that you may want to:
- Select some "rolling shutter propeller" example from the internet and.
- Try to recreate the shape!
- Repeat the first two steps. Just for fun, as long as you like :)