What is a Periscope?

About Periscope:

• It is an optical instrument used in land and sea warfare, submarine navigation, and elsewhere to enable an observer to see his surroundings while remaining undercover, behind armor, or submerged.
• Submarines have periscopes so that people inside can see what is on the surface of the water.

Construction and Working Principle:

• Periscopes can be constructed using a pair of flat mirrors or prisms and a rectangular hollow tube that has a viewing window at the top and bottom of the tube. 
• The mirrors within this structure are fixed at an angle of 45o at the two ends of the rectangular hollow.
• A periscope is a useful example of the law of reflection at work. It’s important that your mirrors are placed at a 45° angle, because light always reflects away from a mirror at the same angle that it hits it. 
• In a periscope, light from an object strikes the top mirror at 45° and bounces off at the same angle. 
• This sends light directly down the tube and onto the lower mirror. This mirror, also at a 45° angle, reflects light directly to your eye. 
• A simple periscope only requires mirrors, whereas a more complicated periscope utilizes prisms rather than mirrors. 
• The periscopes used in submarine applications are complex, typically requiring the use of tubes that are at least 10 meters in length to achieve a greater range of scope.

Q1) What is the Central Scientific Instruments Organisation (CSIO)?

CSIO Chandigarh, is a constituent laboratory of the Council of Scientific & Industrial Research (CSIR), a national laboratory dedicated to research, design and development of scientific and industrial instruments. It is a multi-disciplinary and multi-dimensional apex industrial research & development organization in the country to stimulate growth of the Instrument Industry in India covering a wide range of applications.

Source: In a first, Navy submarine periscope refurbished at CSIO

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