A camera obscura Latin for "dark chamber" is an optical device that led to photography and the camera.
Go into a very dark room on a bright day. Make a small hole in a window cover and look at the opposite wall. What do you see? Magic! There in full color and movement will be the world outside the window — upside down! This magic is explained by a simple law of the physical world. Light travels in a straight line and when some of the rays reflected from a bright subject pass through a small hole in thin material they do not scatter but cross and reform as an upside down image on a flat surface held parallel to the hole. This law of optics was known in ancient times.
A video that explains Camera Obscura.
Class experience:
In class we were able to try camera obscura in a large scale factor of an art classroom. We had blacked out all the entrances of light with black card and tape. Making one hole in the card so only that bit of light would be able to enter the classroom. Unfortunately the British weather was not supporting us, so not enough light was there to make the experiment succeed. Also not being able to tape up all the light gaps in the windows we were not able to block out all the lights.