How does it work?

Movie Projector:

            When you go to the movie theater, you go to see a movie on the “big screen”.  If the movie weren’t on a big screen, then it wouldn’t be as fun to see.  Now the question is, how do you get a movie film projected onto a big screen.  The film can’t be the same size as the screen because that would be vastly inefficient. 

            The key points to consider with this situation, is that the image will be projected onto a big screen.  If the object is projected, then the image formed must be real.  The original is much smaller than the image which will be formed.  Therefore we are looking at a Case 4 situation.  The image formed from the object should be magnified, real and inverted, on the other side of the lens, and beyond 2F.  You may wonder why the image on the big screen is not upside down, and this is because the film is placed into the projector so that it is upside down, that way when it is inverted, it becomes right side up.

Movie Projector Credits: Karen Wu