Question

It is said that the real image is inverted, also it is said that the image formed by the cinema hall is the real image. Why are we not able to see images inverted in a cinema hall?

Answer 1

Hint: When attempting questions like the one given to us above, keep in mind the different concepts regarding concave and convex mirrors and lenses and remember the concepts regarding real and virtual images, erect and inverted images and how and why they are formed and magnified or diminished.

Complete answer:
When we talk about real and virtual images, we first get to know what an image is. Basically an image or picture can be a visual representation of an object which is placed in front of or somewhere ahead of a mirror or lens. Formation of images can be a result of the meeting of sunshine or light rays that are being refracted or reflected consistently with their respective laws.
But one thing to note here is that, these rays do not always meet, rather they just appear in front to produce images. Based on this, if rays meet or simply appear we classify the images thus formed as real and virtual.
Real images are the type of images that are formed due to the convergence of light or sunshine rays at some point after reflected or refracted from a mirror or lens. They are formed with a purpose where light rays undergo interaction with one another and these images are inverted in nature and can be seen on screen.
On the other hand virtual images are pictures which only appear to be formed behind a mirror; however the image isn’t actually present there. In this case of virtual images, when light from an object is allowed to strike the mirror and when light rays are reflected from the mirror then it seems like the rays are diverging somewhere behind the mirror. Here the images formed are always erect as compared to real images which are formed inverted.
Now coming to the reason why we don’t see inverted images in cinema halls is because in cinema halls, the movie projectors use two mirrors. First mirror is used to concentrate the light source and the second mirror is used to focus the images on the screen, hence inverting the images twice , making the final image thus formed erect.

Note: When we talk about image formation by concave and convex mirrors, we also talk about the image formations for concave and convex lenses. So basically convex lenses focus the light rays to a specific point whereas a concave lens diverges the light rays, hence the name of diverging lens while a convex lens is also called converging lens.