An elaboration to clear up some possible confusion for the OP:
"Light-sensitive" means different things:
Panchromatic films are sensitive to all visible wavelengths of light plus some UV. The weakest sensitivity for these films is usually in the green area, hence the possibility of using a weak, dark green safelight for a limited time to inspect a developing negative. The small exposure doesn't expose the film to enough light to fog it. If you expose the film too long to the same safelight, however, it will fog the film, as oldtimermetoo found out. The link above to MichaelandPaula.com is the best guide for developing by inspection that I know of. Most of us prefer to use time/temp. and keep the film in total darkness. (Question: just why do you want to inspect your film while developing anyway?)
Orthochromatic film is sensitive to blue and green (and some UV) but not red. Therefore, it can be processed under a red safelight. Again, even too much "safe" light will fog the film; the safelight needs to be dim enough and the exposure short enough so that the film's exposure threshold is not reached.
Older photo emulsions (think plates/films from the 19th century) are sensitive to only blue and UV. These are usually referred to as "blue-sensitive" and can also be developed under a suitable safelight.
Emulsions on graded photo paper (i.e., not variable-contrast) are like these older emulsions; sensitive to only blue and UV. Safelights for these papers are usually amber or red.
Variable contrast papers are sensitive to blue and green, so an appropriate safelight, usually red, is needed. Amber is sometime used too if the paper's sensitivity allows.
Safelights are rarely 100% safe. They pass other wavelengths in addition to the desired ones. Therefore, it is a good idea to limit the exposure even to a safelight. Safelight tests are a routine part of setting up a darkroom.
Exposed and developed = Image; Exposed and fixed = No Image
Light-sensitive film gets exposed when struck by enough light of the colors it is sensitive too. This makes a latent image. This image needs to be turned into metallic silver somehow before it's visible. There used to be materials that would form a silver image with exposure to light alone (printing out paper or POP), but these are no longer commercially available. Nowadays, you need a chemical developer to do the job.
After the developing step, we stop the chemical reaction with a stop bath. Even though the development is stopped at this point, the film is still light-sensitive. You could expose it to light and put it back in the developer and develop more parts of the film that weren't exposed the first time. It is the fixer that removes the undeveloped, but still light-sensitive silver halides so that the film can't be exposed any more.
Fixer also removes exposed, but undeveloped silver halides. If you take exposed film and put it straight into the fixer, it will come out blank, even if you've exposed it to room light. Theoretically, therefore, you could expose film to light after the stop bath stage with no ill effects. The remaining silver halides will get exposed, but you can then just fix them out, since they are not developed. In practice, most of us keep the film in the dark till at least halfway through the fixing stage for a couple of reasons. First, if the stop is not complete, the remaining active developer will go to work on the newly-exposed silver halides, "solarizing" the image or, worse, fogging it. Second, if the light is strong enough, some film emulsions will fog a bit even without developer. Better to play it safe.
BTW, solarizing prints is used by many printers as a special effect; the print is exposed for a very short time to overall exposure (e.g., turning on the room lights) for a very short time while in the developer tray. Google for some images.
Hope this helps,
Doremus
"Light-sensitive" means different things:
Panchromatic films are sensitive to all visible wavelengths of light plus some UV. The weakest sensitivity for these films is usually in the green area, hence the possibility of using a weak, dark green safelight for a limited time to inspect a developing negative. The small exposure doesn't expose the film to enough light to fog it. If you expose the film too long to the same safelight, however, it will fog the film, as oldtimermetoo found out. The link above to MichaelandPaula.com is the best guide for developing by inspection that I know of. Most of us prefer to use time/temp. and keep the film in total darkness. (Question: just why do you want to inspect your film while developing anyway?)
Orthochromatic film is sensitive to blue and green (and some UV) but not red. Therefore, it can be processed under a red safelight. Again, even too much "safe" light will fog the film; the safelight needs to be dim enough and the exposure short enough so that the film's exposure threshold is not reached.
Older photo emulsions (think plates/films from the 19th century) are sensitive to only blue and UV. These are usually referred to as "blue-sensitive" and can also be developed under a suitable safelight.
Emulsions on graded photo paper (i.e., not variable-contrast) are like these older emulsions; sensitive to only blue and UV. Safelights for these papers are usually amber or red.
Variable contrast papers are sensitive to blue and green, so an appropriate safelight, usually red, is needed. Amber is sometime used too if the paper's sensitivity allows.
Safelights are rarely 100% safe. They pass other wavelengths in addition to the desired ones. Therefore, it is a good idea to limit the exposure even to a safelight. Safelight tests are a routine part of setting up a darkroom.
Exposed and developed = Image; Exposed and fixed = No Image
Light-sensitive film gets exposed when struck by enough light of the colors it is sensitive too. This makes a latent image. This image needs to be turned into metallic silver somehow before it's visible. There used to be materials that would form a silver image with exposure to light alone (printing out paper or POP), but these are no longer commercially available. Nowadays, you need a chemical developer to do the job.
After the developing step, we stop the chemical reaction with a stop bath. Even though the development is stopped at this point, the film is still light-sensitive. You could expose it to light and put it back in the developer and develop more parts of the film that weren't exposed the first time. It is the fixer that removes the undeveloped, but still light-sensitive silver halides so that the film can't be exposed any more.
Fixer also removes exposed, but undeveloped silver halides. If you take exposed film and put it straight into the fixer, it will come out blank, even if you've exposed it to room light. Theoretically, therefore, you could expose film to light after the stop bath stage with no ill effects. The remaining silver halides will get exposed, but you can then just fix them out, since they are not developed. In practice, most of us keep the film in the dark till at least halfway through the fixing stage for a couple of reasons. First, if the stop is not complete, the remaining active developer will go to work on the newly-exposed silver halides, "solarizing" the image or, worse, fogging it. Second, if the light is strong enough, some film emulsions will fog a bit even without developer. Better to play it safe.
BTW, solarizing prints is used by many printers as a special effect; the print is exposed for a very short time to overall exposure (e.g., turning on the room lights) for a very short time while in the developer tray. Google for some images.
Hope this helps,
Doremus