Projector help

So my dyslexia just can’t get around how this works. I have the Panasonic PTAE8000 and a 130” CinemaScope screen.
When the movie is at 2.35:1 the screen is filled without any black lines and when the film changes to 16:9 or IMAX the lens zooms out automatically with black bars to the sides maintaining a constant image height throughout the film. This feature is not available in new projectors and from what I’ve read most people have a 16:9 screen. What happens when watching say Interstellar when the aspect ration switches? Does it extend out beyond the screen or does the projector amend the aspect ratio to fit it onto the screen? I don’t know…..