The kaleidoscope works by using mirrors to reflect light down the tube into your eyes. Creating patterns through reflection. The light is first shone through coloured beads.
Imagine the girl is a coloured bead, she is standing inside a triangle created by three mirrors attached together at the sides, a pattern is created by her reflected images. In the picture below the middle triangle is the mirrors, while the other triangles don't actually exist, they are just the reflection of the beads.
A classic kaleidoscope image looks like the one below, but no kaleidoscope image is the same as another as the images are created by the beads falling while you turn the plastic container attached to the end of the tube in which they are held.
A kaleidoscope generally looks like this.
An consists of the below parts.