What happens after you open a film camera on a shot?

You mean when you expose the film?

Well, if you mean exposing the film, the film is light sensitive (photosensitive). When you take a picture, the camera opens a small amount to let light in. The light reacts with the film, causing it to react wherever the light touches it. In a printed picture, the areas the light touches more are lighter, the areas where the light is blocked by an object are darker. On the negative, the reverse is true.

So if you open film and expose it, the film receives far more light than it ever would through the lens. So the entire frame (and any other film the light touches) react to it by becoming completely dark on the negative, completely blank on the printed picture. Too much light.

Film isn’t safe for viewing in the light until after it has been processed. Part of the process is making the film no longer photosensitive.

Very poorly phrased question. What exactly are you asking?