Describe that a Pixel is a picture element, like a square on a piece of graph paper, where remote sensors record information as numbers. A camera takes light energy and records it chemically on film. The film is then processed and the image transferred to paper where we can look at it. We call this final form a photographic image.
Most films have chemicals that are sensitive to visible light energy.
This means it will record the same images a human eye can see. Scientists have also created very complex detectors that can sense many different wavelengths in the electromagnetic spectrum. These sensitive instruments record the reflected energy as numbers or digits. Sensors record their measurements as numbers from 0 to 255. This digital information is often recorded on magnetic tape, like in a tape recorder or video cassette, or radioed back to Earth.