What is the theory of a periscope?

Hello Abantika, it is based on the phenomenon of reflection or total internal reflection.

We have to have a lengthy tube in vertical position. At the top end a small tube is connected with it in horizontal direction of course facing towards right. At the bottom end a similar tube connected in horizontal but towards left. So it looks like _| sorry not able to draw line at the top right side of vertical line.

Now at the turning region we have to fix two mirrors making an angle of 45 deg with the vertical line.

So as light enters through top tube would fall on the plane mirror at angle of incidence 45 deg. So the reflected ray would go downwards along vertical line and again would hit the lower plane mirror at same 45 deg. So it finally comes out through the bottom tube. So one sitting in a pit would be able to see things on the surface of the land. Same way one in the submarine will be able to see the enemy boats sailing on the water.

Instead plane mirrors as we use prisms then light intensity would be more as there is no loss of light as in the case of plane mirror reflection. Using prism, total internal reflection would be apt phenomenon.

periscope is an instrument used generally divers under water , the objects on the surface of earth.

it works non the principal of light refraction.

take 1 big pipe and two small pipes.place two small mirrors at 45 degrees that is slantly at either ends of big pipe. then connect two small ends at either ends of big pipe. that completes periscope model.

when you see from one end you can see the object at the other end.

the principal is that image of object at the top end fall on top mirror .it gets reflected to the lower mirror. that image can be seen by our eye at lower end.you can see the shape in wikipedia.

rough model can be made even with using agarbathi outer casings

its disadvantage is that it form multiple images