We see just one image of an object placed in front of a mirror. And, we see more than one when the object is placed between two mirrors arranged like a 'V'. In this exhibit, we have three plane mirrors joined to form a triangular prism. Duck into the space and you will see a multitude of yourself ! The many faces you see are formed by reflection of reflections of your image. Such a multiple image forming instrument is called Kaleidoscope.
A person standing in front of a plane mirror can see his image in the mirror.
If two mirrors are hinged together and are kept 1800 apart, even then there will be a single image. (infact it is just as good as having single big plane mirror). If the angle between the mirrors is reduced, we begin to see another image forming and there will be ‘two’ complete images when the angle between the mirrors becomes 1200.
As we further reduce the angle to 900, we will have 'three' complete images. Likewise, we will have 'four' images when the angle is 720, five images at 600 and so on. As the angle between the mirrors is reduced further, the number of images would increase and it can be generalised as follows :-
So, we continue to get complete images as long as the angle between the mirrors divides 3600 completely.
This is known as multiple reflection where the image of the object itself serves as the object for further images.
Kaleidoscope is an instrument which works on the principle of multiple reflection.
It can be made by combining three or more mirrors to form a closed structure.
If three mirrors are used, the closed structure will be just an enclosure like the one seen in this exhibit. Multiple images of the object kept inside the enclosure would be formed leading to beautiful symmetrical patters.
When we say an enclosure made out of three mirrors, it is for sure that the sum of all the angles formed between the mirrors should be 1800. In a usual triangle, the individual angles can have any value. But, here in this triangular arrangement of mirrors, those angles should be such that each of them divides 3600 completely. (i.e. in order to have complete images)
In this exhibit, instead of keeping any other object, people themselves can get inside the triangular arrangement of mirrors and see their own images of images of images.