Imagine you are standing in the middle of a room with no windows, doors or lights. What do you see? Well, nothing because there’s no light. Now imagine you pull out a flashlight and turn it on. The light from the flashlight moves in a straight line. When that beam of light hits an object, the light bounces off that item and into your eyes, allowing you to see whatever is inside the room.
All light behaves just like that flashlight — it travels in a straight line. But, light also bounces off of objects, which is what allows us to see and photograph objects. When light bounces off an object, it continues to travel in a straight line, but it bounces back at the same angle that it comes in at.
That means light rays are essentially bouncing everywhere in all kinds of different directions. The first camera was essentially a room with a small hole on one side wall. Light would pass through that hole, and since it’s reflected in straight lines, the image would be projected on the opposite wall, upside down. While devices like this existed long before true photography, it wasn’t until someone decided to place material that was sensitive to light at the back of that room that photography was born. When light hit the material, which through the course of photography’s history was made up of things from glass to paper, the chemicals reacted to light, etching an image in the surface.