If the cinema screen projects real image and we know real image are always inverted then why the movie to be projected is erect(why we dont see film upside-down)?

Asked by jatin452002 | 8th Jun, 2017, 03:24: PM

Expert Answer:

This is a genuine query with a conceptual backdrop. A cinema projector uses a reel on which light is incident, which is then focussed by a lens to form a real image on the screen. But the thing that has to be understood is that inverted does not mean upside down always. This principle is used in a pinhole camera too. 
 
 
So, the light from reel is focussed on a lens which forms a real inverted image and this light is then sent out from an opening which inverts the image further forming an erect image on the screen.

Answered by Romal Bhansali | 9th Jun, 2017, 09:46: AM