Cameras and our eyes detect light. In each case, they have:
Cameras are devices that focus light from an object onto a photo-sensitive material using a lens. In an old-fashioned camera, the photo-sensitive material was camera film. When the film absorbed light, a chemical change produced an image in the film, called the ‘negative’. This was used to produce a photograph on photo-sensitive paper.
In a modern camera or the camera in a mobile phone, the photo-sensitive material produces electrical impulses, which are used to produce an image file. This can be viewed on the screen, or its information sent to a printer.
Like the camera, the eye focuses light from an object onto a photo-sensitive material. However, in the eye, this material is the retina. The retina contains cells that are sensitive to light. They produce electrical impulses when they absorb light. These impulses are passed along the optic nerve to the brain, which interprets them as vision.