What is camera obscura?
Camera obscura is simply a darkened space e.g. a room or a box, which has a small hole on the wall which allows the outside light in. On the wall opposite the hole you should be able to see whatever image is outside reflected on the wall however it would be upside down(inverted). The image will appear to be upside down because as we know, light travels in straight lines and when the light from outside is travelling through the small hole, the light from the bottom of the image which also travels in a perfectly straight line towards the camera opening, will hit the top of the back of the camera, making the image inside appear to be upside down.
Did you know that the image formed on the retina in our eye is an inverted one(upside down) however a certain part of our brain called the visual cortex where the visual information that our eyes take in is processed, enhanced and reconfigured into the finalized images that we see. This is why some people believe that babies actually see the world upside down as their brain has yet to process the image and to turn it the right side up.
History of the Camera Obscura
The first record of The camera obscura was said to be recorded in Ancient Greece where Aristotle noticed how light passing through a small hole into a room that was completely darkened, produces an image on the wall opposite, that showed the outside of his home. However some people think it goes back to the stone age where the camera obscura produced the first ever art in cave drawings. In the late 13th century camera obscura was used by astronomers to view the sun. In the victorian era, large camera obscures became popular seaside attractions.
What can be seen?
The image that will shown on the opposite wall will be upside down (inverted) and back to front (laterally transposed). The size of the hole has a great effect on the picture that is being projected. A small hole produces a sharp image, which is dim, while a larger hole produces a brighter picture which is less well focused. This happens because light travels in straight lines, a property known as the 'rectilinear propagation' of light.