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Theory:

Devices that works on the principle of multiple reflections:
Certain devices, such as periscopes, bend light and assist in viewing the image of an object that cannot be seen with the naked eye. The principle of a periscope is multiple reflections of light. Mirrors in the barbershop and kaleidoscopes also forms multiple images due to the multiple reflections of light.
Periscopeshutterstock_439908595 (1).png
Kaleidoscopeshutterstock_1252853962 (1).jpg
Mirrors in barbershopshutterstock_1161177124 (1).jpg
  
Periscope:
  • Periscopes are optical devices used to look at objects that are not in the observer's line of sight.
  • There are two mirrors inside the periscope that are inclined at a \(45°\) angle.
  • Submarines, the military, the navy, and nuclear reactors all use periscopes.
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Principle diagram of a periscope
 
Kaleidoscope:
  • Kaleidoscope is a device that works on the principle of multiple reflections with the help of multiple mirrors.
  • It is made up of a cylindrical structure with three plane mirrors inside it that contains several pieces of beads, broken glass, colourful bangles, pebbles.
  • From one end, the observer can see the Kaleidoscope, and from the other end, light enters the Kaleidoscope.
  • When light falls on these objects in the Kaleidoscope, multiple reflections form colourful patterns in the three Mirrors.
Kaleidoscope_tube_1 (1).jpg kaleidoscope-4979634_1920.jpg
Kaleidoscope - Pattern
 
Know the difference between luminous and non-luminous objects:
 
Luminous
Non-luminous objects
Objects that can emit light energy by themselves are known as luminous objects.Objects that cannot emit light energy by themselves are known as non-luminous objects.
Example:
Sun and candle
Example:
Moon and trees
MaxPixel.net-Bulb-Electricity-Electric-Bulb-Electric-Light-Lamp-160207.png
Electric bulb
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Tree
Reference:
https://pixabay.com/illustrations/tree-elevation-landscape-5373563/
https://www.maxpixel.net/Bulb-Electricity-Electric-Bulb-Electric-Light-Lamp-160207
https://pixabay.com/photos/kaleidoscope-energy-mandala-lsd-4979634/
https://commons.wikimedia.org/wiki/File:Kaleidoscope_tube_1.jpg